Point cloud data transmission device, point cloud data transmission method, point cloud data reception device, and point cloud data reception method

ABSTRACT

Disclosed herein are a point cloud data transmission method including encoding point cloud data, and transmitting point cloud data, and a point cloud data reception method including receiving point cloud data, decoding the point cloud data, and rendering the point cloud data.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/226,748, filed on Apr. 9, 2021, which claims the benefit of U.S.Provisional Application No. 63/008,735, filed on Apr. 11, 2020. Thecontents of which are hereby incorporated by reference in theirentirety.

BACKGROUND OF THE DISCLOSURE Field of the Disclosure

Embodiments provide a method for providing point cloud content toprovide a user with various services such as virtual reality (VR),augmented reality (AR), mixed reality (MR), and self-driving services.

Discussion of the Related Art

A point cloud is a set of points in a three-dimensional (3D) space. Itis difficult to generate point cloud data because the number of pointsin the 3D space is large.

A large throughput is required to transmit and receive data of a pointcloud.

SUMMARY OF THE DISCLOSURE

An object of the present disclosure is to provide a point cloud datatransmission device, a point cloud data transmission method, a pointcloud data reception device, and a point cloud data reception method forefficiently transmitting and receiving a point cloud.

Another object of the present disclosure is to provide a point clouddata transmission device, a point cloud data transmission method, apoint cloud data reception device, and a point cloud data receptionmethod for addressing latency and encoding/decoding complexity.

Embodiments are not limited to the above-described objects, and thescope of the embodiments may be extended to other objects that can beinferred by those skilled in the art based on the entire contents of thepresent disclosure.

To achieve these objects and other advantages and in accordance with thepurpose of the disclosure, as embodied and broadly described herein, amethod for transmitting point cloud data may include encoding pointcloud data, encapsulating the point cloud data, and transmitting thepoint cloud data.

In another aspect of the present disclosure, a method for receivingpoint cloud data may include receiving point cloud data, decapsulatingthe point cloud data, and decoding the point cloud data.

The point cloud data transmission method, the point cloud datatransmission device, the point cloud data reception method, and thepoint cloud data reception apparatus according to the embodiments mayprovide a good-quality point cloud service.

The point cloud data transmission method, the point cloud datatransmission device, the point cloud data reception method, and thepoint cloud data reception apparatus according to the embodiments mayachieve various video codec methods.

The point cloud data transmission method, the point cloud datatransmission device, the point cloud data reception method, and thepoint cloud data reception apparatus according to the embodiments mayprovide universal point cloud content such as a self-driving service.

It is to be understood that both the foregoing general description andthe following detailed description of the present disclosure areexemplary and explanatory and are intended to provide furtherexplanation of the disclosure as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the disclosure andtogether with the description serve to explain the principle of thedisclosure. In the drawings:

FIG. 1 illustrates an exemplary structure of a transmission/receptionsystem for providing point cloud content according to embodiments;

FIG. 2 illustrates capture of point cloud data according to embodiments;

FIG. 3 illustrates an exemplary point cloud, geometry, and texture imageaccording to embodiments;

FIG. 4 illustrates an exemplary V-PCC encoding process according toembodiments;

FIG. 5 illustrates an example of a tangent plane and a normal vector ofa surface according to embodiments;

FIG. 6 illustrates an exemplary bounding box of a point cloud accordingto embodiments;

FIG. 7 illustrates an example of determination of individual patchpositions on an occupancy map according to embodiments;

FIG. 8 shows an exemplary relationship among normal, tangent, andbitangent axes according to embodiments;

FIG. 9 shows an exemplary configuration of the minimum mode and maximummode of a projection mode according to embodiments;

FIG. 10 illustrates an exemplary EDD code according to embodiments;

FIG. 11 illustrates an example of recoloring based on color values ofneighboring points according to embodiments;

FIG. 12 illustrates an example of push-pull background filling accordingto embodiments;

FIG. 13 shows an exemplary possible traversal order for a 4*4 blockaccording to embodiments;

FIG. 14 illustrates an exemplary best traversal order according toembodiments;

FIG. 15 illustrates an exemplary 2D video/image encoder according toembodiments;

FIG. 16 illustrates an exemplary V-PCC decoding process according toembodiments;

FIG. 17 shows an exemplary 2D video/image decoder according toembodiments;

FIG. 18 is a flowchart illustrating operation of a transmission deviceaccording to embodiments of the present disclosure;

FIG. 19 is a flowchart illustrating operation of a reception deviceaccording to embodiments;

FIG. 20 illustrates an exemplary architecture for V-PCC based storageand streaming of point cloud data according to embodiments;

FIG. 21 is an exemplary block diagram of a device for storing andtransmitting point cloud data according to embodiments;

FIG. 22 is an exemplary block diagram of a point cloud data receptiondevice according to embodiments;

FIG. 23 illustrates an exemplary structure operable in connection withpoint cloud data transmission/reception methods/devices according toembodiments;

FIG. 24 illustrates a V-PCC bitstream according to embodiments;

FIG. 25 illustrates an example of a V-PCC bitstream according toembodiments;

FIG. 26 shows a V-PCC unit and a V-PCC unit header according toembodiments;

FIG. 27 shows exemplary syntax of a V-PCC parameter set according toembodiments;

FIG. 28 shows an atlas frame according to embodiments;

FIG. 29 shows an exemplary atlas substream according to embodiments;

FIG. 30 shows exemplary syntax of an atlas sequence parameter setaccording to embodiments;

FIG. 31 shows exemplary syntax of an atlas frame parameter set accordingto embodiments;

FIG. 32 shows exemplary syntax of atlas frame tile information accordingto embodiments;

FIG. 33 shows exemplary syntax of an atlas adaptation parameter set andatlas camera parameters according to embodiments;

FIG. 34 shows atlas tile group layer information according toembodiments;

FIG. 35 shows reference list structure information according toembodiments;

FIG. 36 shows an atlas tile group data unit according to embodiments;

FIG. 37 shows exemplary syntax of a patch data unit according toembodiments;

FIG. 38 shows a structure of a file carrying point cloud data accordingto embodiments;

FIG. 39 shows a structure of a file carrying point cloud data accordingto embodiments;

FIG. 40 shows an exemplary operation of encapsulating point cloud dataand metadata related to the point cloud data according to embodiments;

FIG. 41 shows an exemplary SEI message structure according toembodiments;

FIG. 42 shows VPCC SEI message structure information and atlas aparameter set structure according to embodiments;

FIG. 43 shows VPCC SEI message structure information and atlas aparameter set structure according to embodiments;

FIG. 44 illustrates a method for an SEI track group and SEI entitygrouping according to embodiments;

FIG. 45 illustrates a method for atlas parameter set track grouping (SEItrack group) and atlas parameter set entity grouping (SEI entitygrouping) according to embodiments;

FIG. 46 shows an example of a V-PCC sample entry and a V-PCC bitstreamsample entry (VPCCBitstreamSampleEntry) according to embodiments;

FIG. 47 shows syntax of a V-PCC SEI sample and/or a V-PCC APS sample bya timed metadata track according to embodiments;

FIG. 48 shows exemplary syntax of a V-PCC SEI item property and a V-PCCAPS item property according to embodiments;

FIG. 49 is a flowchart illustrating a method of transmitting point clouddata according to embodiments; and

FIG. 50 is a flowchart illustrating a method of receiving point clouddata according to embodiments.

DETAILED DESCRIPTION OF THE DISCLOSURE

Best Mode

Reference will now be made in detail to the preferred embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings. The detailed description, which will be givenbelow with reference to the accompanying drawings, is intended toexplain exemplary embodiments of the present disclosure, rather than toshow the only embodiments that can be implemented according to thepresent disclosure. The following detailed description includes specificdetails in order to provide a thorough understanding of the presentdisclosure. However, it will be apparent to those skilled in the artthat the present disclosure may be practiced without such specificdetails.

Although most terms used in the present disclosure have been selectedfrom general ones widely used in the art, some terms have beenarbitrarily selected by the applicant and their meanings are explainedin detail in the following description as needed. Thus, the presentdisclosure should be understood based upon the intended meanings of theterms rather than their simple names or meanings.

FIG. 1 illustrates an exemplary structure of a transmission/receptionsystem for providing point cloud content according to embodiments.

The present disclosure provides a method of providing point cloudcontent to provide a user with various services such as virtual reality(VR), augmented reality (AR), mixed reality (MR), and autonomousdriving. The point cloud content according to the embodiments representdata representing objects as points, and may be referred to as a pointcloud, point cloud data, point cloud video data, point cloud image data,or the like.

A point cloud data transmission device 10000 according to embodiment mayinclude a point cloud video acquirer 10001, a point cloud video encoder10002, a file/segment encapsulation module 10003, and/or a transmitter(or communication module) 10004. The transmission device according tothe embodiments may secure and process point cloud video (or point cloudcontent) and transmit the same. According to embodiments, thetransmission device may include a fixed station, a base transceiversystem (BTS), a network, an artificial intelligence (AI) device and/orsystem, a robot, and an AR/VR/XR device and/or a server. According toembodiments, the transmission device 10000 may include a device robot, avehicle, AR/VR/XR devices, a portable device, a home appliance, anInternet of Thing (IoT) device, and an AI device/server which areconfigured to perform communication with a base station and/or otherwireless devices using a radio access technology (e.g., 5G New RAT (NR),Long Term Evolution (LTE)).

The point cloud video acquirer 10001 according to the embodimentsacquires a point cloud video through a process of capturing,synthesizing, or generating a point cloud video.

The point cloud video encoder 10002 according to the embodiments encodesthe point cloud video data. According to embodiments, the point cloudvideo encoder 10002 may be referred to as a point cloud encoder, a pointcloud data encoder, an encoder, or the like. The point cloud compressioncoding (encoding) according to the embodiments is not limited to theabove-described embodiment. The point cloud video encoder may output abitstream containing the encoded point cloud video data. The bitstreammay include not only the encoded point cloud video data, but alsosignaling information related to encoding of the point cloud video data.

The encoder according to the embodiments may support both thegeometry-based point cloud compression (G-PCC) encoding scheme and/orthe video-based point cloud compression (V-PCC) encoding scheme. Inaddition, the encoder may encode a point cloud (referring to eitherpoint cloud data or points) and/or signaling data related to the pointcloud. The specific operation of encoding according to embodiments willbe described below.

As used herein, the term V-PCC may stand for Video-based Point CloudCompression (V-PCC). The term V-PCC may be the same as Visual VolumetricVideo-based Coding (V3C). These terms may be complementarily used.

The file/segment encapsulation module 10003 according to the embodimentsencapsulates the point cloud data in the form of a file and/or segmentform. The point cloud data transmission method/device according to theembodiments may transmit the point cloud data in a file and/or segmentform.

The transmitter (or communication module) 10004 according to theembodiments transmits the encoded point cloud video data in the form ofa bitstream. According to embodiments, the file or segment may betransmitted to a reception device over a network, or stored in a digitalstorage medium (e.g., USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc.). Thetransmitter according to the embodiments is capable of wired/wirelesscommunication with the reception device (or the receiver) over a networkof 4G, 5G, 6G, etc. In addition, the transmitter may perform necessarydata processing operation according to the network system (e.g., a 4G,5G or 6G communication network system). The transmission device maytransmit the encapsulated data in an on-demand manner.

A point cloud data reception device 10005 according to the embodimentsmay include a receiver 10006, a file/segment decapsulation module 10007,a point cloud video decoder 10008, and/or a renderer 10009. According toembodiments, the reception device may include a device robot, a vehicle,AR/VR/XR devices, a portable device, a home appliance, an Internet ofThing (IoT) device, and an AI device/server which are configured toperform communication with a base station and/or other wireless devicesusing a radio access technology (e.g., 5G New RAT (NR), Long TermEvolution (LTE)).

The receiver 10006 according to the embodiments receives a bitstreamcontaining point cloud video data. According to embodiments, thereceiver 10006 may transmit feedback information to the point cloud datatransmission device 10000.

The file/segment decapsulation module 10007 decapsulates a file and/or asegment containing point cloud data. The decapsulation module accordingto the embodiments may perform an reverse process of the encapsulationprocess according to the embodiments.

The point cloud video decoder 10007 decodes the received point cloudvideo data. The decoder according to the embodiments may perform areverse process of encoding according to the embodiments.

The renderer 10009 renders the decoded point cloud video data. Accordingto embodiments, the renderer 10009 may transmit the feedback informationobtained at the reception side to the point cloud video decoder 10008.The point cloud video data according to the embodiments may carryfeedback information to the receiver. According to embodiments, thefeedback information received by the point cloud transmission device maybe provided to the point cloud video encoder.

The arrows indicated by dotted lines in the drawing represent atransmission path of feedback information acquired by the receptiondevice 10005. The feedback information is information for reflectinginteractivity with a user who consumes point cloud content, and includesuser information (e.g., head orientation information), viewportinformation, and the like). In particular, when the point cloud contentis content for a service (e.g., autonomous driving service, etc.) thatrequires interaction with a user, the feedback information may beprovided to the content transmitting side (e.g., the transmission device10000) and/or the service provider. According to embodiments, thefeedback information may be used in the reception device 10005 as wellas the transmission device 10000, and may not be provided.

The head orientation information according to embodiments is informationabout a user's head position, orientation, angle, motion, and the like.The reception device 10005 according to the embodiments may calculateviewport information based on the head orientation information. Theviewport information may be information about a region of the pointcloud video that the user is viewing. A viewpoint is a point where auser is viewing a point cloud video, and may refer to a center point ofthe viewport region. That is, the viewport is a region centered on theviewpoint, and the size and shape of the region may be determined by afield of view (FOV). Accordingly, the reception device 10005 may extractthe viewport information based on a vertical or horizontal FOV supportedby the device in addition to the head orientation information. Inaddition, the reception device 10005 performs gaze analysis to check howthe user consumes a point cloud, a region that the user gazes at in thepoint cloud video, a gaze time, and the like. According to embodiments,the reception device 10005 may transmit feedback information includingthe result of the gaze analysis to the transmission device 10000. Thefeedback information according to the embodiments may be acquired in therendering and/or display process. The feedback information according tothe embodiments may be secured by one or more sensors included in thereception device 10005. In addition, according to embodiments, thefeedback information may be secured by the renderer 10009 or a separateexternal element (or device, component, etc.). The dotted lines in FIG.1 represent a process of transmitting the feedback information securedby the renderer 10009. The point cloud content providing system mayprocess (encode/decode) point cloud data based on the feedbackinformation. Accordingly, the point cloud video data decoder 10008 mayperform a decoding operation based on the feedback information. Thereception device 10005 may transmit the feedback information to thetransmission device. The transmission device (or the point cloud videodata encoder 10002) may perform an encoding operation based on thefeedback information. Accordingly, the point cloud content providingsystem may efficiently process necessary data (e.g., point cloud datacorresponding to the user's head position) based on the feedbackinformation rather than processing (encoding/decoding) all point clouddata, and provide point cloud content to the user.

According to embodiments, the transmission device 10000 may be called anencoder, a transmission device, a transmitter, or the like, and thereception device 10004 may be called a decoder, a reception device, areceiver, or the like.

The point cloud data processed in the point cloud content providingsystem of FIG. 1 according to embodiments (through a series of processesof acquisition/encoding/transmission/decoding/rendering) may be referredto as point cloud content data or point cloud video data. According toembodiments, the point cloud content data may be used as a conceptcovering metadata or signaling information related to point cloud data.

The elements of the point cloud content providing system illustrated inFIG. 1 may be implemented by hardware, software, a processor, and/orcombinations thereof.

Embodiments may provide a method of providing point cloud content toprovide a user with various services such as virtual reality (VR),augmented reality (AR), mixed reality (MR), and autonomous driving.

In order to provide a point cloud content service, a point cloud videomay be acquired first. The acquired point cloud video may be transmittedthrough a series of processes, and the reception side may process thereceived data back into the original point cloud video and render theprocessed point cloud video. Thereby, the point cloud video may beprovided to the user. Embodiments provide a method of effectivelyperforming this series of processes.

The entire processes for providing a point cloud content service (thepoint cloud data transmission method and/or point cloud data receptionmethod) may include an acquisition process, an encoding process, atransmission process, a decoding process, a rendering process, and/or afeedback process.

According to embodiments, the process of providing point cloud content(or point cloud data) may be referred to as a point cloud compressionprocess. According to embodiments, the point cloud compression processmay represent a geometry-based point cloud compression process.

Each element of the point cloud data transmission device and the pointcloud data reception device according to the embodiments may behardware, software, a processor, and/or a combination thereof.

In order to provide a point cloud content service, a point cloud videomay be acquired. The acquired point cloud video is transmitted through aseries of processes, and the reception side may process the receiveddata back into the original point cloud video and render the processedpoint cloud video. Thereby, the point cloud video may be provided to theuser. Embodiments provide a method of effectively performing this seriesof processes.

The entire processes for providing a point cloud content service mayinclude an acquisition process, an encoding process, a transmissionprocess, a decoding process, a rendering process, and/or a feedbackprocess.

The point cloud compression system may include a transmission device anda reception device. The transmission device may output a bitstream byencoding a point cloud video, and deliver the same to the receptiondevice through a digital storage medium or a network in the form of afile or a stream (streaming segment). The digital storage medium mayinclude various storage media such as a USB, SD, CD, DVD, Blu-ray, HDD,and SSD.

The transmission device may include a point cloud video acquirer, apoint cloud video encoder, a file/segment encapsulator, and atransmitter. The reception device may include a receiver, a file/segmentdecapsulator, a point cloud video decoder, and a renderer. The encodermay be referred to as a point cloud video/picture/picture/frame encoder,and the decoder may be referred to as a point cloudvideo/picture/picture/frame decoding device. The transmitter may beincluded in the point cloud video encoder. The receiver may be includedin the point cloud video decoder. The renderer may include a display.The renderer and/or the display may be configured as separate devices orexternal components. The transmission device and the reception devicemay further include a separate internal or externalmodule/unit/component for the feedback process.

According to embodiments, the operation of the reception device may bethe reverse process of the operation of the transmission device.

The point cloud video acquirer may perform the process of acquiringpoint cloud video through a process of capturing, composing, orgenerating point cloud video. In the acquisition process, data of 3Dpositions (x, y, z)/attributes (color, reflectance, transparency, etc.)of multiple points, for example, a polygon file format (PLY) (or thestanford triangle format) file may be generated. For a video havingmultiple frames, one or more files may be acquired. During the captureprocess, point cloud related metadata (e.g., capture related metadata)may be generated.

A point cloud data transmission device according to embodiments mayinclude an encoder configured to encode point cloud data, and atransmitter configured to transmit the point cloud data. The data may betransmitted in the form of a bitstream containing a point cloud.

A point cloud data reception device according to embodiments may includea receiver configured to receive point cloud data, a decoder configuredto decode the point cloud data, and a renderer configured to render thepoint cloud data.

The method/device according to the embodiments represents the pointcloud data transmission device and/or the point cloud data receptiondevice.

FIG. 2 illustrates capture of point cloud data according to embodiments.

Point cloud data according to embodiments may be acquired by a camera orthe like. A capturing technique according to embodiments may include,for example, inward-facing and/or outward-facing.

In the inward-facing according to the embodiments, one or more camerasinwardly facing an object of point cloud data may photograph the objectfrom the outside of the object.

In the outward-facing according to the embodiments, one or more camerasoutwardly facing an object of point cloud data may photograph theobject. For example, according to embodiments, there may be fourcameras.

The point cloud data or the point cloud content according to theembodiments may be a video or a still image of an object/environmentrepresented in various types of 3D spaces. According to embodiments, thepoint cloud content may include video/audio/an image of an object.

For capture of point cloud content, a combination of camera equipment (acombination of an infrared pattern projector and an infrared camera)capable of acquiring depth and RGB cameras capable of extracting colorinformation corresponding to the depth information may be configured.Alternatively, the depth information may be extracted through LiDAR,which uses a radar system that measures the location coordinates of areflector by emitting a laser pulse and measuring the return time. Ashape of the geometry consisting of points in a 3D space may beextracted from the depth information, and an attribute representing thecolor/reflectance of each point may be extracted from the RGBinformation. The point cloud content may include information about thepositions (x, y, z) and color (YCbCr or RGB) or reflectance (r) of thepoints. For the point cloud content, the outward-facing technique ofcapturing an external environment and the inward-facing technique ofcapturing a central object may be used. In the VR/AR environment, whenan object (e.g., a core object such as a character, a player, a thing,or an actor) is configured into point cloud content that may be viewedby the user in any direction (360 degrees), the configuration of thecapture camera may be based on the inward-facing technique. When thecurrent surrounding environment is configured into point cloud contentin a mode of a vehicle, such as autonomous driving, the configuration ofthe capture camera may be based on the outward-facing technique. Becausethe point cloud content may be captured by multiple cameras, a cameracalibration process may need to be performed before the content iscaptured to configure a global coordinate system for the cameras.

The point cloud content may be a video or still image of anobject/environment presented in various types of 3D spaces.

Additionally, in the point cloud content acquisition method, any pointcloud video may be composed based on the captured point cloud video.Alternatively, when a point cloud video for a computer-generated virtualspace is to be provided, capturing with an actual camera may not beperformed. In this case, the capture process may be replaced simply by aprocess of generating related data.

Post-processing may be needed for the captured point cloud video toimprove the quality of the content. In the video capture process, themaximum/minimum depth may be adjusted within a range provided by thecamera equipment. Even after the adjustment, point data of an unwantedarea may still be present. Accordingly, post-processing of removing theunwanted area (e.g., the background) or recognizing a connected spaceand filling the spatial holes may be performed. In addition, pointclouds extracted from the cameras sharing a spatial coordinate systemmay be integrated into one piece of content through the process oftransforming each point into a global coordinate system based on thecoordinates of the location of each camera acquired through acalibration process. Thereby, one piece of point cloud content having awide range may be generated, or point cloud content with a high densityof points may be acquired.

The point cloud video encoder may encode the input point cloud videointo one or more video streams. One video may include a plurality offrames, each of which may correspond to a still image/picture. In thisspecification, a point cloud video may include a point cloudimage/frame/picture/video/audio. In addition, the term “point cloudvideo” may be used interchangeably with a point cloudimage/frame/picture. The point cloud video encoder may perform avideo-based point cloud compression (V-PCC) procedure. The point cloudvideo encoder may perform a series of procedures such as prediction,transformation, quantization, and entropy coding for compression andencoding efficiency. The encoded data (encoded video/image information)may be output in the form of a bitstream. Based on the V-PCC procedure,the point cloud video encoder may encode point cloud video by dividingthe same into a geometry video, an attribute video, an occupancy mapvideo, and auxiliary information, which will be described later. Thegeometry video may include a geometry image, the attribute video mayinclude an attribute image, and the occupancy map video may include anoccupancy map image. The auxiliary information may include auxiliarypatch information. The attribute video/image may include a texturevideo/image.

The encapsulation processor (file/segment encapsulation module) 1003 mayencapsulate the encoded point cloud video data and/or metadata relatedto the point cloud video in the form of, for example, a file. Here, themetadata related to the point cloud video may be received from themetadata processor. The metadata processor may be included in the pointcloud video encoder or may be configured as a separate component/module.The encapsulation processor may encapsulate the data in a file formatsuch as ISOBMFF or process the same in the form of a DASH segment or thelike. According to an embodiment, the encapsulation processor mayinclude the point cloud video-related metadata in the file format. Thepoint cloud video metadata may be included, for example, in boxes atvarious levels on the ISOBMFF file format or as data in a separate trackwithin the file. According to an embodiment, the encapsulation processormay encapsulate the point cloud video-related metadata into a file. Thetransmission processor may perform processing for transmission on thepoint cloud video data encapsulated according to the file format. Thetransmission processor may be included in the transmitter or may beconfigured as a separate component/module. The transmission processormay process the point cloud video data according to a transmissionprotocol. The processing for transmission may include processing fordelivery over a broadcast network and processing for delivery through abroadband. According to an embodiment, the transmission processor mayreceive point cloud video-related metadata from the metadata processoralown with the point cloud video data, and perform processing of thepoint cloud video data for transmission.

The transmitter 1004 may transmit the encoded video/image information ordata that is output in the form of a bitstream to the receiver of thereception device through a digital storage medium or a network in theform of a file or streaming. The digital storage medium may includevarious storage media such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD.The transmitter may include an element for generating a media file in apredetermined file format, and may include an element for transmissionover a broadcast/communication network. The receiver may extract thebitstream and transmit the extracted bitstream to the decoding device.

The receiver 1003 may receive point cloud video data transmitted by thepoint cloud video transmission device according to the presentdisclosure. Depending on the transmission channel, the receiver mayreceive the point cloud video data over a broadcast network or through abroadband. Alternatively, the point cloud video data may be receivedthrough a digital storage medium.

The reception processor may process the received point cloud video dataaccording to the transmission protocol. The reception processor may beincluded in the receiver or may be configured as a separatecomponent/module. The reception processor may reversely perform theabove-described process of the transmission processor suchthat theprocessing corresponds to the processing for transmission performed atthe transmission side. The reception processor may deliver the acquiredpoint cloud video data to the decapsulation processor, and the acquiredpoint cloud video-related metadata to the metadata parser. The pointcloud video-related metadata acquired by the reception processor maytake the form of a signaling table.

The decapsulation processor (file/segment decapsulation module) 1007 maydecapsulate the point cloud video data received in the form of a filefrom the reception processor. The decapsulation processor maydecapsulate the files according to ISOBMFF or the like, and may acquirea point cloud video bitstream or point cloud video-related metadata (ametadata bitstream). The acquired point cloud video bitstream may bedelivered to the point cloud video decoder, and the acquired point cloudvideo-related metadata (metadata bitstream) may be delivered to themetadata processor. The point cloud video bitstream may include themetadata (metadata bitstream). The metadata processor may be included inthe point cloud video decoder or may be configured as a separatecomponent/module. The point cloud video-related metadata acquired by thedecapsulation processor may take the form of a box or a track in thefile format. The decapsulation processor may receive metadata necessaryfor decapsulation from the metadata processor, when necessary. The pointcloud video-related metadata may be delivered to the point cloud videodecoder and used in a point cloud video decoding procedure, or may betransferred to the renderer and used in a point cloud video renderingprocedure.

The point cloud video decoder may receive the bitstream and decode thevideo/image by performing an operation corresponding to the operation ofthe point cloud video encoder. In this case, the point cloud videodecoder may decode the point cloud video by dividing the same into ageometry video, an attribute video, an occupancy map video, andauxiliary information as described below. The geometry video may includea geometry image, and the attribute video may include an attributeimage. The occupancy map video may include an occupancy map image. Theauxiliary information may include auxiliary patch information. Theattribute video/image may include a texture video/image.

The 3D geometry may be reconstructed based on the decoded geometryimage, the occupancy map, and auxiliary patch information, and then maybe subjected to a smoothing process. A color point cloud image/picturemay be reconstructed by assigning color values to the smoothed 3Dgeometry based on the texture image. The renderer may render thereconstructed geometry and the color point cloud image/picture. Therendered video/image may be displayed through the display. The user mayview all or part of the rendered result through a VR/AR display or atypical display.

The feedback process may include transferring various kinds of feedbackinformation that may be acquired in the rendering/displaying process tothe transmission side or to the decoder of the reception side.Interactivity may be provided through the feedback process in consumingpoint cloud video. According to an embodiment, head orientationinformation, viewport information indicating a region currently viewedby a user, and the like may be delivered to the transmission side in thefeedback process. According to an embodiment, the user may interact withthings implemented in the VR/AR/MR/autonomous driving environment. Inthis case, information related to the interaction may be delivered tothe transmission side or a service provider during the feedback process.According to an embodiment, the feedback process may be skipped.

The head orientation information may represent information about thelocation, angle and motion of a user's head. On the basis of thisinformation, information about a region of the point cloud videocurrently viewed by the user, that is, viewport information, may becalculated.

The viewport information may be information about a region of the pointcloud video currently viewed by the user. Gaze analysis may be performedusing the viewport information to check the way the user consumes thepoint cloud video, a region of the point cloud video at which the usergazes, and how long the user gazes at the region. The gaze analysis maybe performed at the reception side and the result of the analysis may bedelivered to the transmission side on a feedback channel. A device suchas a VR/AR/MR display may extract a viewport region based on thelocation/direction of the user's head, vertical or horizontal FOVsupported by the device, and the like.

According to an embodiment, the aforementioned feedback information maynot only be delivered to the transmission side, but also be consumed atthe reception side. That is, decoding and rendering processes at thereception side may be performed based on the aforementioned feedbackinformation. For example, only the point cloud video for the regioncurrently viewed by the user may be preferentially decoded and renderedbased on the head orientation information and/or the viewportinformation.

Here, the viewport or viewport region may represent a region of thepoint cloud video currently viewed by the user. A viewpoint is a pointwhich is viewed by the user in the point cloud video and may represent acenter point of the viewport region. That is, a viewport is a regionaround a viewpoint, and the size and form of the region may bedetermined by the field of view (FOV).

The present disclosure relates to point cloud video compression asdescribed above. For example, the methods/embodiments disclosed in thepresent disclosure may be applied to the point cloud compression orpoint cloud coding (PCC) standard of the moving picture experts group(MPEG) or the next generation video/image coding standard.

As used herein, a picture/frame may generally represent a unitrepresenting one image in a specific time interval.

A pixel or a pel may be the smallest unit constituting one picture (orimage). Also, “sample” may be used as a term corresponding to a pixel. Asample may generally represent a pixel or a pixel value. It mayrepresent only a pixel/pixel value of a luma component, only apixel/pixel value of a chroma component, or only a pixel/pixel value ofa depth component.

A unit may represent a basic unit of image processing. The unit mayinclude at least one of a specific region of the picture and informationrelated to the region. The unit may be used interchangeably with termsuch as block or area in some cases. In a general case, an M×N block mayinclude samples (or a sample array) or a set (or array) of transformcoefficients configured in M columns and N rows.

FIG. 3 illustrates an example of a point cloud, a geometry image, and atexture image according to embodiments.

A point cloud according to the embodiments may be input to the V-PCCencoding process of FIG. 4 , which will be described later, to generatea geometry image and a texture image. According to embodiments, a pointcloud may have the same meaning as point cloud data.

As shown in the figure, the left part shows a point cloud, in which anobject is positioned in a 3D space and may be represented by a boundingbox or the like. The middle part shows the geometry, and the right partshows a texture image (non-padded image).

Video-based point cloud compression (V-PCC) according to embodiments mayprovide a method of compressing 3D point cloud data based on a 2D videocodec such as HEVC or VVC. Data and information that may be generated inthe V-PCC compression process are as follows:

Occupancy map: this is a binary map indicating whether there is data ata corresponding position in a 2D plane, using a value of 0 or 1 individing the points constituting a point cloud into patches and mappingthe same to the 2D plane. The occupancy map may represent a 2D arraycorresponding to ATLAS, and the values of the occupancy map may indicatewhether each sample position in the atlas corresponds to a 3D point.ATLAS means an object including information about 2D patches for eachpoint cloud frame. For example, ATLAS may include 2D arrangement andsize of patches, the position of a corresponding 3D region within a 3Dpoint, a projection plan, and a level of detail parameters.

An atlas is a collection of 2D bounding boxes positioned in arectangular frame that correspond to a 3D bounding box in a 3D space inwhich volumetric data is rendered and information related thereto.

The atlas bitstream is a bitstream for one or more atlas framesconstituting an atlas and related data.

The atlas frame is a 2D rectangular array of atlas samples onto whichpatches are projected. An atlas sample is a position of a rectangularframe onto which patches associated with the atlas are projected.

An atlas frame may be partitioned into tiles. A tile is a unit in whicha 2D frame is partioned. That is, a tile is a unit for partitioningsignaling information of point cloud data called an atlas.

Patch: A set of points constituting a point cloud, which indicates thatpoints belonging to the same patch are adjacent to each other in 3Dspace and are mapped in the same direction among 6-face bounding boxplanes in the process of mapping to a 2D image.

A patch is a unit in which a tile partitioned. The patch is signalinginformation on the configuration of point cloud data.

The reception device according to the embodiments may restore attributevideo data, geometry video data, and occupancy video data, which areactual video data having the same presentation time, based on an atlas(tile, patch).

Geometry image: this is an image in the form of a depth map thatpresents position information (geometry) about each point constituting apoint cloud on a patch-by-patch basis. The geometry image may becomposed of pixel values of one channel. Geometry represents a set ofcoordinates associated with a point cloud frame.

Texture image: this is an image representing the color information abouteach point constituting a point cloud on a patch-by-patch basis. Atexture image may be composed of pixel values of a plurality of channels(e.g., three channels of R, G, and B). The texture is included in anattribute. According to embodiments, a texture and/or attribute may beinterpreted as the same object and/or having an inclusive relationship.

Auxiliary patch info: this indicates metadata needed to reconstruct apoint cloud with individual patches. Auxiliary patch info may includeinformation about the position, size, and the like of a patch in a 2D/3Dspace.

Point cloud data according to the embodiments, for example, V-PCCcomponents may include an atlas, an accuracy map, geometry, andattributes.

Atlas represents a set of 2D bounding boxes. It may be patches, forexample, patches projected onto a rectangular frame. Atlas maycorrespond to a 3D bounding box in a 3D space, and may represent asubset of a point cloud.

An attribute may represent a scalar or vector associated with each pointin the point cloud. For example, the attributes may include color,reflectance, surface normal, time stamps, material ID.

The point cloud data according to the embodiments represents PCC dataaccording to video-based point cloud compression (V-PCC) scheme. Thepoint cloud data may include a plurality of components. For example, itmay include an occupancy map, a patch, geometry and/or texture.

FIG. 4 illustrates a V-PCC encoding process according to embodiments.

The figure illustrates a V-PCC encoding process for generating andcompressing an occupancy map, a geometry image, a texture image, andauxiliary patch information. The V-PCC encoding process of FIG. 4 may beprocessed by the point cloud video encoder 10002 of FIG. 1 . Eachelement of FIG. 4 may be performed by software, hardware, processorand/or a combination thereof.

The patch generation or patch generator 40000 receives a point cloudframe (which may be in the form of a bitstream containing point clouddata). The patch generator 40000 generates a patch from the point clouddata. In addition, patch information including information about patchgeneration is generated.

The patch packing or patch packer 40001 packs patches for point clouddata. For example, one or more patches may be packed. In addition, thepatch packer generates an occupancy map containing information aboutpatch packing.

The geometry image generation or geometry image generator 40002generates a geometry image based on the point cloud data, patches,and/or packed patches. The geometry image refers to data containinggeometry related to the point cloud data.

The texture image generation or texture image generator 40003 generatesa texture image based on the point cloud data, patches, and/or packedpatches. In addition, the texture image may be generated further basedon smoothed geometry generated by smoothing processing of smoothingbased on the patch information.

The smoothing or smoother 40004 may mitigate or eliminate errorscontained in the image data. For example, based on the patchedreconstructed geometry image, portions that may cause errors betweendata may be smoothly filtered out to generate smoothed geometry.

The auxiliary patch info compression or auxiliary patch info compressor40005, auxiliary patch information related to the patch informationgenerated in the patch generation is compressed. In addition, thecompressed auxiliary patch information may be transmitted to themultiplexer. The auxiliary patch information may be used in the geometryimage generation 40002.

The image padding or image padder 40006, 40007 may pad the geometryimage and the texture image, respectively. The padding data may bepadded to the geometry image and the texture image.

The group dilation or group dilator 40008 may add data to the textureimage in a similar manner to image padding. The added data may beinserted into the texture image.

The video compression or video compressor 40009, 40010, 40011 maycompress the padded geometry image, the padded texture image, and/or theoccupancy map, respectively. The compression may encode geometryinformation, texture information, occupancy information, and the like.

The entropy compression or entropy compressor 40012 may compress (e.g.,encode) the occupancy map based on an entropy scheme.

According to embodiments, the entropy compression and/or videocompression may be performed, respectively depending on whether thepoint cloud data is lossless and/or lossy.

The multiplexer 40013 multiplexes the compressed geometry image, thecompressed texture image, and the compressed occupancy map into abitstream.

The specific operations in the respective processes of FIG. 4 aredescribed below.

Patch Generation 40000

The patch generation process refers to a process of dividing a pointcloud into patches, which are mapping units, in order to map the pointcloud to the 2D image. The patch generation process may be divided intothree steps: normal value calculation, segmentation, and patchsegmentation.

The normal value calculation process will be described in detail withreference to FIG. 5 .

FIG. 5 illustrates an example of a tangent plane and a normal vector ofa surface according to embodiments.

The surface of FIG. 5 is used in the patch generation process 40000 ofthe V-PCC encoding process of FIG. 4 as follows.

Normal Calculation Related to Patch Generation:

Each point of a point cloud has its own direction, which is representedby a 3D vector called a normal vector. Using the neighbors of each pointobtained using a K-D tree or the like, a tangent plane and a normalvector of each point constituting the surface of the point cloud asshown in the figure may be obtained. The search range applied to theprocess of searching for neighbors may be defined by the user.

The tangent plane refers to a plane that passes through a point on thesurface and completely includes a tangent line to the curve on thesurface.

FIG. 6 illustrates an exemplary bounding box of a point cloud accordingto embodiments.

A method/device according to embodiments, for example, patch generation,may employ a bounding box in generating a patch from point cloud data.

The bounding box according to the embodiments refers to a box of a unitfor dividing point cloud data based on a hexahedron in a 3D space.

The bounding box may be used in the process of projecting a targetobject of the point cloud data onto a plane of each planar face of ahexahedron in a 3D space. The bounding box may be generated andprocessed by the point cloud video acquirer 10000 and the point cloudvideo encoder 10002 of FIG. 1 . Further, based on the bounding box, thepatch generation 40000, patch packing 40001, geometry image generation40002, and texture image generation 40003 of the V-PCC encoding processof FIG. 2 may be performed.

Segmentation Related to Patch Generation

Segmentation is divided into two processes: initial segmentation andrefine segmentation.

The point cloud encoder 10002 according to the embodiments projects apoint onto one face of a bounding box. Specifically, each pointconstituting a point cloud is projected onto one of the six faces of abounding box surrounding the point cloud as shown in the figure. Initialsegmentation is a process of determining one of the planar faces of thebounding box onto which each point is to be projected.

{right arrow over (n)}_(pi) _(dx) , which is a normal valuecorresponding to each of the six planar faces, is defined as follows:

-   -   (1.0, 0.0, 0.0), (0.0, 1.0, 0.0), (0.0, 0.0, 1.0), (−1.0, 0.0,        0.0), (0.0, −1.0, 0.0), (0.0, 0.0, −1.0).

As shown in the equation below, a face that yields the maximum value ofdot product of the normal vector {right arrow over (n)}_(p) _(i) of eachpoint, which is obtained in the normal value calculation process, and{right arrow over (n)}_(pi) _(dx) is determined as a projection plane ofthe corresponding point. That is, a plane whose normal vector is mostsimilar to the direction of the normal vector of a point is determinedas the projection plane of the point.

$\max\limits_{p_{idx}}\left\{ {{\overset{\rightarrow}{n}}_{{pi}^{1}} \cdot {\overset{\rightarrow}{n}}_{Pidx}} \right\}$

The determined plane may be identified by one cluster index, which isone of 0 to 5.

Refine segmentation is a process of enhancing the projection plane ofeach point constituting the point cloud determined in the initialsegmentation process in consideration of the projection planes ofneighboring points. In this process, a score normal, which representsthe degree of similarity between the normal vector of each point and thenormal of each planar face of the bounding box which are considered indetermining the projection plane in the initial segmentation process,and score smooth, which indicates the degree of similarity between theprojection plane of the current point and the projection planes ofneighboring points, may be considered together.

Score smooth may be considered by assigning a weight to the scorenormal. In this case, the weight value may be defined by the user. Therefine segmentation may be performed repeatedly, and the number ofrepetitions may also be defined by the user.

Patch Segmentation Related to Patch Generation

Patch segmentation is a process of dividing the entire point cloud intopatches, which are sets of neighboring points, based on the projectionplane information about each point constituting the point cloud obtainedin the initial/refine segmentation process. The patch segmentation mayinclude the following steps:

-   -   1) Calculate neighboring points of each point constituting the        point cloud, using the K-D tree or the like. The maximum number        of neighbors may be defined by the user;    -   2) When the neighboring points are projected onto the same plane        as the current point (when they have the same cluster index),        extract the current point and the neighboring points as one        patch;    -   3) Calculate geometry values of the extracted patch. The details        are described below; and    -   4) Repeat operations 2) to 4) until there is no unextracted        point.

The occupancy map, geometry image and texture image for each patch aswell as the size of each patch are determined through the patchsegmentation process.

FIG. 7 illustrates an example of determination of individual patchpositions on an occupancy map according to embodiments.

The point cloud encoder 10002 according to the embodiments may performpatch packing and generate an accuracy map.

Patch Packing & Occupancy Map Generation (40001)

This is a process of determining the positions of individual patches ina 2D image to map the segmented patches to the 2D image. The occupancymap, which is a kind of 2D image, is a binary map that indicates whetherthere is data at a corresponding position, using a value of 0 or 1. Theoccupancy map is composed of blocks and the resolution thereof may bedetermined by the size of the block. For example, when the block is 1*1block, a pixel-level resolution is obtained. The occupancy packing blocksize may be determined by the user.

The process of determining the positions of individual patches on theoccupancy map may be configured as follows:

-   -   1) Set all positions on the occupancy map to 0;    -   2) Place a patch at a point (u, v) having a horizontal        coordinate within the range of (0, occupancySizeU−patch.sizeU0)        and a vertical coordinate within the range of (0,        occupancySizeV−patch.sizeV0) in the occupancy map plane;    -   3) Set a point (x, y) having a horizontal coordinate within the        range of (0, patch.sizeU0) and a vertical coordinate within the        range of (0, patch.sizeV0) in the patch plane as a current        point;    -   4) Change the position of point (x, y) in raster order and        repeat operations 3) and 4) if the value of coordinate (x, y) on        the patch occupancy map is 1 (there is data at the point in the        patch) and the value of coordinate (u+x, v+y) on the global        occupancy map is 1 (the occupancy map is filled with the        previous patch). Otherwise, proceed to operation 6);    -   5) Change the position of (u, v) in raster order and repeat        operations 3) to 5);    -   6) Determine (u, v) as the position of the patch and copy the        occupancy map data about the patch onto the corresponding        portion on the global occupancy map; and    -   7) Repeat operations 2) to 7) for the next patch.    -   occupancySizeU: indicates the width of the occupancy map. The        unit thereof is occupancy packing block size.    -   occupancySizeV: indicates the height of the occupancy map. The        unit thereof is occupancy packing block size.    -   patch.sizeU0: indicates the width of the occupancy map. The unit        thereof is occupancy packing block size.    -   patch.sizeV0: indicates the height of the occupancy map. The        unit thereof is occupancy packing block size.

For example, as shown in FIG. 7 , there is a box corresponding to apatch having a patch size in a box corresponding to an occupancy packingsize block, and a point (x, y) may be located in the box.

FIG. 8 shows an exemplary relationship among normal, tangent, andbitangent axes according to embodiments.

The point cloud encoder 10002 according to embodiments may generate ageometry image. The geometry image refers to image data includinggeometry information about a point cloud. The geometry image generationprocess may employ three axes (normal, tangent, and bitangent) of apatch in FIG. 8 .

Geometry Image Generation (40002)

In this process, the depth values constituting the geometry images ofindividual patchs are determined, and the entire geometry image isgenerated based on the positions of the patches determined in the patchpacking process described above. The process of determining the depthvalues constituting the geometry images of individual patches may beconfigured as follows.

-   -   1) Calculate parameters related to the position and size of an        individual patch. The parameters may include the following        information.

A normal index indicating the normal axis is obtained in the previouspatch generation process. The tangent axis is an axis coincident withthe horizontal axis u of the patch image among the axes perpendicular tothe normal axis, and the bitangent axis is an axis coincident with thevertical axis v of the patch image among the axes perpendicular to thenormal axis. The three axes may be expressed as shown in the figure.

FIG. 9 shows an exemplary configuration of the minimum mode and maximummode of a projection mode according to embodiments.

The point cloud encoder 10002 according to embodiments may performpatch-based projection to generate a geometry image, and the projectionmode according to the embodiments includes a minimum mode and a maximummode.

3D spatial coordinates of a patch may be calculated based on thebounding box of the minimum size surrounding the patch. For example, the3D spatial coordinates may include the minimum tangent value of thepatch (on the patch 3d shift tangent axis) of the patch, the minimumbitangent value of the patch (on the patch 3d shift bitangent axis), andthe minimum normal value of the patch (on the patch 3d shift normalaxis).

2D size of a patch indicates the horizontal and vertical sizes of thepatch when the patch is packed into a 2D image. The horizontal size(patch 2d size u) may be obtained as a difference between the maximumand minimum tangent values of the bounding box, and the vertical size(patch 2d size v) may be obtained as a difference between the maximumand minimum bitangent values of the bounding box.

-   -   2) Determine a projection mode of the patch. The projection mode        may be either the min mode or the max mode. The geometry        information about the patch is expressed with a depth value.        When each point constituting the patch is projected in the        normal direction of the patch, two layers of images, an image        constructed with the maximum depth value and an image        constructed with the minimum depth value, may be generated.

In the min mode, in generating the two layers of images d0 and d1, theminimum depth may be configured for d0, and the maximum depth within thesurface thickness from the minimum depth may be configured for d1, asshown in the figure.

For example, when a point cloud is located in 2D as illustrated in thefigure, there may be a plurality of patches including a plurality ofpoints. As shown in the figure, it is indicated that points marked withthe same style of shadow may belong to the same patch. The figureillustrates the process of projecting a patch of points marked withblanks.

When projecting points marked with blanks to the left/right, the depthmay be incremented by 1 as 0, 1, 2, . . . , 6, 7, 8, 9 with respect tothe left side, and the number for calculating the depths of the pointsmay be marked on the right side.

The same projection mode may be applied to all point clouds or differentprojection modes may be applied to respective frames or patchesaccording to user definition. When different projection modes areapplied to the respective frames or patches, a projection mode that mayenhance compression efficiency or minimize missed points may beadaptively selected.

-   -   3) Calculate the Depth Values of the Individual Points.

In the min mode, image d0 is constructed with depth0 which is a valueobtained by subtracting the minimum normal value of the patch (on thepatch 3d shift normal axis) calculated in operation 1) from the minimumnormal value of the patch (on the patch 3d shift normal axis) for theminimum normal value of each point. If there is another depth valuewithin the range between depth0 and the surface thickness at the sameposition, this value is set to depth1. Otherwise, the value of depth0 isassigned to depth1. Image d1 is constructed with the value of depth1.

For example, a minimum value may be calculated in determining the depthof points of image d0 (4 2 4 4 0 6 0 0 9 9 0 8 0). In determining thedepth of points of image d1, a greater value among two or more pointsmay be calculated. When only one point is present, the value thereof maybe calculated (4 4 4 4 6 6 6 8 9 9 8 8 9). In the process of encodingand reconstructing the points of the patch, some points may be lost (Forexample, in the figure, eight points are lost).

In the max mode, image d0 is constructed with depth0 which is a valueobtained by subtracting the minimum normal value of the patch (on thepatch 3d shift normal axis) calculated in operation 1) from the minimumnormal value of the patch (on the patch 3d shift normal axis) for themaximum normal value of each point. If there is another depth valuewithin the range between depth0 and the surface thickness at the sameposition, this value is set to depth1. Otherwise, the value of depth0 isassigned to depth1. Image d1 is constructed with the value of depth1.

For example, a maximum value may be calculated in determining the depthof points of d0 (4 4 4 4 6 6 6 8 9 9 8 8 9). In addition, in determiningthe depth of points of d1, a lower value among two or more points may becalculated. When only one point is present, the value thereof may becalculated (4 2 4 4 5 6 0 6 9 9 0 8 0). In the process of encoding andreconstructing the points of the patch, some points may be lost (Forexample, in the figure, six points are lost).

The entire geometry image may be generated by placing the geometryimages of the individual patches generated through the above-describedprocesses onto the entire geometry image based on the patch positioninformation determined in the patch packing process.

Layer d1 of the generated entire geometry image may be encoded usingvarious methods. A first method (absolute d1 method) is to encode thedepth values of the previously generated image d1. A second method(differential method) is to encode a difference between the depth valuesof previously generated image d1 and the depth values of image d0.

In the encoding method using the depth values of the two layers, d0 andd1 as described above, if there is another point between the two depths,the geometry information about the point is lost in the encodingprocess, and therefore an enhanced-delta-depth (EDD) code may be usedfor lossless coding.

Hereinafter, the EDD code will be described in detail with reference toFIG. 10 .

FIG. 10 illustrates an exemplary EDD code according to embodiments.

In some/all processes of the point cloud encoder 10002 and/or V-PCCencoding (e.g., video compression 40009), the geometry information aboutpoints may be encoded based on the EOD code.

As shown in the figure, the EDD code is used for binary encoding of thepositions of all points within the range of surface thickness includingd1. For example, in the figure, the points included in the second leftcolumn may be represented by an EDD code of 0b1001 (=9) because thepoints are present at the first and fourth positions over D0 and thesecond and third positions are empty. When the EDD code is encodedtogether with D0 and transmitted, a reception terminal may restore thegeometry information about all points without loss.

For example, when there is a point present above a reference point, thevalue is 1. When there is no point, the value is 0. Thus, the code maybe expressed based on 4 bits.

Smoothing (40004)

Smoothing is an operation for eliminating discontinuity that may occuron the patch boundary due to deterioration of the image qualityoccurring during the compression process. Smoothing may be performed bythe point cloud encoder or smoother:

-   -   1) Reconstruct the point cloud from the geometry image. This        operation may be the reverse of the geometry image generation        described above. For example, the reverse process of encoding        may be reconstructed;    -   2) Calculate neighboring points of each point constituting the        reconstructed point cloud using the K-D tree or the like;    -   3) Determine whether each of the points is positioned on the        patch boundary. For example, when there is a neighboring point        having a different projection plane (cluster index) from the        current point, it may be determined that the point is positioned        on the patch boundary;    -   4) If there is a point present on the patch boundary, move the        point to the center of mass of the neighboring points        (positioned at the average x, y, z coordinates of the        neighboring points). That is, change the geometry value.        Otherwise, maintain the previous geometry value.

FIG. 11 illustrates an example of recoloring based on color values ofneighboring points according to embodiments.

The point cloud encoder or the texture image generator 40003 accordingto the embodiments may generate a texture image based on recoloring.

Texture Image Generation (40003)

The texture image generation process, which is similar to the geometryimage generation process described above, includes generating textureimages of individual patches and generating an entire texture image byarranging the texture images at determined positions. However, in theoperation of generating texture images of individual patches, an imagewith color values (e.g., R, G, and B values) of the points constitutinga point cloud corresponding to a position is generated in place of thedepth values for geometry generation.

In estimating a color value of each point constituting the point cloud,the geometry previously obtained through the smoothing process may beused. In the smoothed point cloud, the positions of some points may havebeen shifted from the original point cloud, and accordingly a recoloringprocess of finding colors suitable for the changed positions may berequired. Recoloring may be performed using the color values ofneighboring points. For example, as shown in the figure, a new colorvalue may be calculated in consideration of the color value of thenearest neighboring point and the color values of the neighboringpoints.

For example, referring to the figure, in the recoloring, a suitablecolor value for a changed position may be calculated based on theaverage of the attribute information about the closest original pointsto a point and/or the average of the attribute information about theclosest original positions to the point.

Texture images may also be generated in two layers of t0 and t1, likethe geometry images, which are generated in two layers of d0 and d1.

Auxiliary patch info compression (40005)

The point cloud encoder or the auxiliary patch info compressor accordingto the embodiments may compress the auxiliary patch information(auxiliary information about the point cloud).

The auxiliary patch info compressor compresses the auxiliary patchinformation generated in the patch generation, patch packing, andgeometry generation processes described above. The auxiliary patchinformation may include the following parameters:

-   -   Index (cluster index) for identifying the projection plane        (normal plane);    -   3D spatial position of a patch, i.e., the minimum tangent value        of the patch (on the patch 3d shift tangent axis), the minimum        bitangent value of the patch (on the patch 3d shift bitangent        axis), and the minimum normal value of the patch (on the patch        3d shift normal axis);    -   2D spatial position and size of the patch, i.e., the horizontal        size (patch 2d size u), the vertical size (patch 2d size v), the        minimum horizontal value (patch 2d shift u), and the minimum        vertical value (patch 2d shift u); and    -   Mapping information about each block and patch, i.e., a        candidate index (when patches are disposed in order based on the        2D spatial position and size information about the patches,        multiple patches may be mapped to one block in an overlapping        manner. In this case, the mapped patches constitute a candidate        list, and the candidate index indicates the position in        sequential order of a patch whose data is present in the block),        and a local patch index (which is an index indicating one of the        patches present in the frame). Table X shows a pseudo code        representing the process of matching between blocks and patches        based on the candidate list and the local patch indexes.

The maximum number of candidate lists may be defined by a user.

TABLE 1-1 Pseudo code for mapping a block to a patch   for( i = 0; i <BlockCount; i++ ) {  if( candidatePatches[ i ].size( ) = = 1 ) {  blockToPatch[ i ] = candidatePatches[ i ][ 0 ]  } else {  candidate_index   if( candidate_index = = max_candidate_count ) {   blockToPatch[ i ] = local_patch_index   } else {    blockToPatch[ i ]= candidatePatches[ i ][ candidate_index ]   }  }  }

FIG. 12 illustrates push-pull background filling according toembodiments.

Image padding and group dilation (40006, 40007, 40008)

The image padder according to the embodiments may fill the space exceptthe patch area with meaningless supplemental data based on the push-pullbackground filling technique.

Image padding is a process of filling the space other than the patchregion with meaningless data to improve compression efficiency. Forimage padding, pixel values in columns or rows close to a boundary inthe patch may be copied to fill the empty space. Alternatively, as shownin the figure, a push-pull background filling method may be used.According to this method, the empty space is filled with pixel valuesfrom a low resolution image in the process of gradually reducing theresolution of a non-padded image and increasing the resolution again.

Group dilation is a process of filling the empty spaces of a geometryimage and a texture image configured in two layers, d0/d1 and t0/t1,respectively. In this process, the empty spaces of the two layerscalculated through image padding are filled with the average of thevalues for the same position.

FIG. 13 shows an exemplary possible traversal order for a 4*4 blockaccording to embodiments.

Occupancy Map Compression (40012, 40011)

The occupancy map compressor according to the embodiments may compressthe previously generated occupancy map. Specifically, two methods,namely video compression for lossy compression and entropy compressionfor lossless compression, may be used. Video compression is describedbelow.

The entropy compression may be performed through the followingoperations.

-   -   1) If a block constituting an occupancy map is fully occupied,        encode 1 and repeat the same operation for the next block of the        occupancy map. Otherwise, encode 0 and perform operations 2) to        5).    -   2) Determine the best traversal order to perform run-length        coding on the occupied pixels of the block. The figure shows        four possible traversal orders for a 4*4 block.

FIG. 14 illustrates an exemplary best traversal order according toembodiments.

As described above, the entropy compressor according to the embodimentsmay code (encode) a block based on the traversal order scheme asdescribed above.

For example, the best traversal order with the minimum number of runs isselected from among the possible traversal orders and the index thereofis encoded. The figure illustrates a case where the third traversalorder in FIG. 13 is selected. In the illustrated case, the number ofruns may be minimized to 2, and therefore the third traversal order maybe selected as the best traversal order.

-   -   3) Encode the number of runs. In the example of FIG. 14 , there        are two runs, and therefore 2 is encoded.    -   4) Encode the occupancy of the first run. In the example of FIG.        14 , 0 is encoded because the first run corresponds to        unoccupied pixels.    -   5) Encode lengths of the individual runs (as many as the number        of runs). In the example of FIG. 14 , the lengths of the first        run and the second run, 6 and 10, are sequentially encoded.

Video Compression (40009, 40010, 40011)

The video compressor according to the embodiments encodes a sequence ofa geometry image, a texture image, an occupancy map image, and the likegenerated in the above-described operations, using a 2D video codec suchas HEVC or VVC.

FIG. 15 illustrates an exemplary 2D video/image encoder according toembodiments.

The figure, which represents an embodiment to which the videocompression or video compressor 40009, 40010, and 40011 described aboveis applied, is a schematic block diagram of a 2D video/image encoder15000 configured to encode a video/image signal. The 2D video/imageencoder 15000 may be included in the point cloud video encoder describedabove or may be configured as an internal/external component. Eachcomponent of FIG. 15 may correspond to software, hardware, processorand/or a combination thereof.

Here, the input image may include the geometry image, the texture image(attribute(s) image), and the occupancy map image described above. Theoutput bitstream (i.e., the point cloud video/image bitstream) of thepoint cloud video encoder may include output bitstreams for therespective input images (i.e., the geometry image, the texture image(attribute(s) image), the occupancy map image, etc.).

An inter-predictor 15090 and an intra-predictor 15100 may becollectively called a predictor. That is, the predictor may include theinter-predictor 15090 and the intra-predictor 15100. A transformer15030, a quantizer 15040, an inverse quantizer 15050, and an inversetransformer 15060 may be included in the residual processor. Theresidual processor may further include a subtractor 15020. According toan embodiment, the image splitter 15010, the subtractor 15020, thetransformer 15030, the quantizer 15040, the inverse quantizer 15050, theinverse transformer 15060, the adder 155, the filter 15070, theinter-predictor 15090, the intra-predictor 15100, and the entropyencoder 15110 described above may be configured by one hardwarecomponent (e.g., an encoder or a processor). In addition, the memory15080 may include a decoded picture buffer (DPB) and may be configuredby a digital storage medium.

The image splitter 15010 may spit an image (or a picture or a frame)input to the encoder 15000 into one or more processing units. Forexample, the processing unit may be called a coding unit (CU). In thiscase, the CU may be recursively split from a coding tree unit (CTU) or alargest coding unit (LCU) according to a quad-tree binary-tree (QTBT)structure. For example, one CU may be split into a plurality of CUs of alower depth based on a quad-tree structure and/or a binary-treestructure. In this case, for example, the quad-tree structure may beapplied first and the binary-tree structure may be applied later.Alternatively, the binary-tree structure may be applied first. Thecoding procedure according to the present disclosure may be performedbased on a final CU that is not split anymore. In this case, the LCU maybe used as the final CU based on coding efficiency according tocharacteristics of the image. When necessary, a CU may be recursivelysplit into CUs of a lower depth, and a CU of the optimum size may beused as the final CU. Here, the coding procedure may include prediction,transformation, and reconstruction, which will be described later. Asanother example, the processing unit may further include a predictionunit (PU) or a transform unit (TU). In this case, the PU and the TU maybe split or partitioned from the aforementioned final CU. The PU may bea unit of sample prediction, and the TU may be a unit for deriving atransform coefficient and/or a unit for deriving a residual signal fromthe transform coefficient.

The term “unit” may be used interchangeably with terms such as block orarea. In a general case, an M×N block may represent a set of samples ortransform coefficients configured in M columns and N rows. A sample maygenerally represent a pixel or a value of a pixel, and may indicate onlya pixel/pixel value of a luma component, or only a pixel/pixel value ofa chroma component. “Sample” may be used as a term corresponding to apixel or a pel in one picture (or image).

The encoder 15000 may generate a residual signal (residual block orresidual sample array) by subtracting a prediction signal (predictedblock or predicted sample array) output from the inter-predictor 15090or the intra-predictor 15100 from an input image signal (original blockor original sample array), and the generated residual signal istransmitted to the transformer 15030. In this case, as shown in thefigure, the unit that subtracts the prediction signal (predicted blockor predicted sample array) from the input image signal (original blockor original sample array) in the encoder 15000 may be called asubtractor 15020. The predictor may perform prediction for a processingtarget block (hereinafter referred to as a current block) and generate apredicted block including prediction samples for the current block. Thepredictor may determine whether intra-prediction or inter-prediction isapplied on a current block or CU basis. As will be described later inthe description of each prediction mode, the predictor may generatevarious kinds of information about prediction, such as prediction modeinformation, and deliver the generated information to the entropyencoder 15110. The information about the prediction may be encoded andoutput in the form of a bitstream by the entropy encoder 15110.

The intra-predictor 15100 may predict the current block with referenceto the samples in the current picture. The samples may be positioned inthe neighbor of or away from the current block depending on theprediction mode. In intra-prediction, the prediction modes may include aplurality of non-directional modes and a plurality of directional modes.The non-directional modes may include, for example, a DC mode and aplanar mode. The directional modes may include, for example, 33directional prediction modes or 65 directional prediction modesaccording to fineness of the prediction directions. However, this ismerely an example, and more or fewer directional prediction modes may beused depending on the setting. The intra-predictor 15100 may determine aprediction mode to be applied to the current block, based on theprediction mode applied to the neighboring block.

The inter-predictor 15090 may derive a predicted block for the currentblock based on a reference block (reference sample array) specified by amotion vector on the reference picture. In this case, in order to reducethe amount of motion information transmitted in the inter-predictionmode, the motion information may be predicted on a per block, subblock,or sample basis based on the correlation in motion information betweenthe neighboring blocks and the current block. The motion information mayinclude a motion vector and a reference picture index. The motioninformation may further include information about an inter-predictiondirection (L0 prediction, L1 prediction, Bi prediction, etc.). In thecase of inter-prediction, the neighboring blocks may include a spatialneighboring block, which is present in the current picture, and atemporal neighboring block, which is present in the reference picture.The reference picture including the reference block may be the same asor different from the reference picture including the temporalneighboring block. The temporal neighboring block may be referred to asa collocated reference block or a collocated CU (colCU), and thereference picture including the temporal neighboring block may bereferred to as a collocated picture (colPic). For example, theinter-predictor 15090 may configure a motion information candidate listbased on the neighboring blocks and generate information indicating acandidate to be used to derive a motion vector and/or a referencepicture index of the current block. Inter-prediction may be performedbased on various prediction modes. For example, in a skip mode and amerge mode, the inter-predictor 15090 may use motion information about aneighboring block as motion information about the current block. In theskip mode, unlike the merge mode, the residual signal may not betransmitted. In a motion vector prediction (MVP) mode, the motion vectorof a neighboring block may be used as a motion vector predictor and themotion vector difference may be signaled to indicate the motion vectorof the current block.

The prediction signal generated by the inter-predictor 15090 or theintra-predictor 15100 may be used to generate a reconstruction signal orto generate a residual signal.

The transformer 15030 may generate transform coefficients by applying atransformation technique to the residual signal. For example, thetransformation technique may include at least one of discrete cosinetransform (DCT), discrete sine transform (DST), Karhunen-Loève transform(KLT), graph-based transform (GBT), or conditionally non-lineartransform (CNT). Here, the GBT refers to transformation obtained from agraph depicting the relationship between pixels. The CNT refers totransformation obtained based on a prediction signal generated based onall previously reconstructed pixels. In addition, the transformationoperation may be applied to pixel blocks having the same size of asquare, or may be applied to blocks of a variable size other than thesquare.

The quantizer 15040 may quantize the transform coefficients and transmitthe same to the entropy encoder 15110. The entropy encoder 15110 mayencode the quantized signal (information about the quantized transformcoefficients) and output a bitstream of the encoded signal. Theinformation about the quantized transform coefficients may be referredto as residual information. The quantizer 15040 may rearrange thequantized transform coefficients, which are in a block form, in the formof a one-dimensional vector based on a coefficient scan order, andgenerate information about the quantized transform coefficients based onthe quantized transform coefficients in the form of the one-dimensionalvector. The entropy encoder 15110 may employ various encoding techniquessuch as, for example, exponential Golomb, context-adaptive variablelength coding (CAVLC), and context-adaptive binary arithmetic coding(CABAC). The entropy encoder 15110 may encode information necessary forvideo/image reconstruction (e.g., values of syntax elements) togetherwith or separately from the quantized transform coefficients. Theencoded information (e.g., encoded video/image information) may betransmitted or stored in the form of a bitstream on a networkabstraction layer (NAL) unit basis. The bitstream may be transmittedover a network or may be stored in a digital storage medium. Here, thenetwork may include a broadcast network and/or a communication network,and the digital storage medium may include various storage media such asUSB, SD, CD, DVD, Blu-ray, HDD, and SSD. A transmitter (not shown) totransmit the signal output from the entropy encoder 15110 and/or astorage (not shown) to store the signal may be configured asinternal/external elements of the encoder 15000. Alternatively, thetransmitter may be included in the entropy encoder 15110.

The quantized transform coefficients output from the quantizer 15040 maybe used to generate a prediction signal. For example, inversequantization and inverse transform may be applied to the quantizedtransform coefficients through the inverse quantizer 15050 and theinverse transformer 15060 to reconstruct the residual signal (residualblock or residual samples). The adder 155 may add the reconstructedresidual signal to the prediction signal output from the inter-predictor15090 or the intra-predictor 15100. Thereby, a reconstructed signal(reconstructed picture, reconstructed block, reconstructed sample array)may be generated. When there is no residual signal for a processingtarget block as in the case where the skip mode is applied, thepredicted block may be used as the reconstructed block. The adder 155may be called a reconstructor or a reconstructed block generator. Thegenerated reconstructed signal may be used for intra-prediction of thenext processing target block in the current picture, or may be used forinter-prediction of the next picture through filtering as describedbelow.

The filter 15070 may improve subjective/objective image quality byapplying filtering to the reconstructed signal. For example, the filter15070 may generate a modified reconstructed picture by applying variousfiltering techniques to the reconstructed picture, and the modifiedreconstructed picture may be stored in the memory 15080, specifically,the DPB of the memory 15080. The various filtering techniques mayinclude, for example, deblocking filtering, sample adaptive offset,adaptive loop filtering, and bilateral filtering. As described below inthe description of the filtering techniques, the filter 15070 maygenerate various kinds of information about filtering and deliver thegenerated information to the entropy encoder 15110. The informationabout filtering may be encoded and output in the form of a bitstream bythe entropy encoder 15110.

The modified reconstructed picture transmitted to the memory 15080 maybe used as a reference picture by the inter-predictor 15090. Thus, wheninter-prediction is applied, the encoder may avoid prediction mismatchbetween the encoder 15000 and the decoder and improve encodingefficiency.

The DPB of the memory 15080 may store the modified reconstructed pictureso as to be used as a reference picture by the inter-predictor 15090.The memory 15080 may store the motion information about a block fromwhich the motion information in the current picture is derived (orencoded) and/or the motion information about the blocks in a picturethat has already been reconstructed. The stored motion information maybe delivered to the inter-predictor 15090 so as to be used as motioninformation about a spatial neighboring block or motion informationabout a temporal neighboring block. The memory 15080 may store thereconstructed samples of the reconstructed blocks in the current pictureand deliver the reconstructed samples to the intra-predictor 15100.

At least one of the prediction, transform, and quantization proceduresdescribed above may be skipped. For example, for a block to which thepulse coding mode (PCM) is applied, the prediction, transform, andquantization procedures may be skipped, and the value of the originalsample may be encoded and output in the form of a bitstream.

FIG. 16 illustrates an exemplary V-PCC decoding process according toembodiments.

The V-PCC decoding process or V-PCC decoder may follow the reverseprocess of the V-PCC encoding process (or encoder) of FIG. 4 . Eachcomponent in FIG. 16 may correspond to software, hardware, a processor,and/or a combination thereof.

The demultiplexer 16000 demultiplexes the compressed bitstream to outputa compressed texture image, a compressed geometry image, a compressedoccupancy map, and a compressed auxiliary patch information.

The video decompression or video decompressor 16001, 16002 decompresses(or decodes) each of the compressed texture image and the compressedgeometry image.

The occupancy map decompression or occupancy map decompressor 16003decompresses the compressed occupancy map.

The auxiliary patch info decompression or auxiliary patch infodecompressor 16004 decompresses auxiliary patch information.

The geometry reconstruction or geometry reconstructor 16005 restores(reconstructs) the geometry information based on the decompressedgeometry image, the decompressed occupancy map, and/or the decompressedauxiliary patch information. For example, the geometry changed in theencoding process may be reconstructed.

The smoothing or smoother 16006 may apply smoothing to the reconstructedgeometry. For example, smoothing filtering may be applied.

The texture reconstruction or texture reconstructor 16007 reconstructsthe texture from the decompressed texture image and/or the smoothedgeometry.

The color smoothing or color smoother 16008 smooths color values fromthe reconstructed texture. For example, smoothing filtering may beapplied.

As a result, reconstructed point cloud data may be generated.

The figure illustrates a decoding process of the V-PCC forreconstructing a point cloud by decoding the compressed occupancy map,geometry image, texture image, and auxiliary path information. Eachprocess according to the embodiments is operated as follows.

Video decompression (1600, 16002)

Video decompression is a reverse process of the video compressiondescribed above. In video decompression, a 2D video codec such as HEVCor VVC is used to decode a compressed bitstream containing the geometryimage, texture image, and occupancy map image generated in theabove-described process.

FIG. 17 illustrates an exemplary 2D video/image decoder according toembodiments.

The 2D video/image decoder may follow the reverse process of the 2Dvideo/image encoder of FIG. 15 .

The 2D video/image decoder of FIG. 17 is an embodiment of the videodecompression or video decompressor of FIG. 16 . FIG. 17 is a schematicblock diagram of a 2D video/image decoder 17000 by which decoding of avideo/image signal is performed. The 2D video/image decoder 17000 may beincluded in the point cloud video decoder of FIG. 1 , or may beconfigured as an internal/external component. Each component in FIG. 17may correspond to software, hardware, a processor, and/or a combinationthereof.

Here, the input bitstream may include bitstreams for the geometry image,texture image (attribute(s) image), and occupancy map image describedabove. The reconstructed image (or the output image or the decodedimage) may represent a reconstructed image for the geometry image,texture image (attribute(s) image), and occupancy map image describedabove.

Referring to the figure, an inter-predictor 17070 and an intra-predictor17080 may be collectively referred to as a predictor. That is, thepredictor may include the inter-predictor 17070 and the intra-predictor17080. An inverse quantizer 17020 and an inverse transformer 17030 maybe collectively referred to as a residual processor. That is, theresidual processor may include the inverse quantizer 17020 and theinverse transformer 17030. The entropy decoder 17010, the inversequantizer 17020, the inverse transformer 17030, the adder 17040, thefilter 17050, the inter-predictor 17070, and the intra-predictor 17080described above may be configured by one hardware component (e.g., adecoder or a processor) according to an embodiment. In addition, thememory 170 may include a decoded picture buffer (DPB) or may beconfigured by a digital storage medium.

When a bitstream containing video/image information is input, thedecoder 17000 may reconstruct an image in a process corresponding to theprocess in which the video/image information is processed by the encoderof FIGS. 0.2-1 . For example, the decoder 17000 may perform decodingusing a processing unit applied in the encoder. Thus, the processingunit of decoding may be, for example, a CU. The CU may be split from aCTU or an LCU along a quad-tree structure and/or a binary-treestructure. Then, the reconstructed video signal decoded and outputthrough the decoder 17000 may be played through a player.

The decoder 17000 may receive a signal output from the encoder in theform of a bitstream, and the received signal may be decoded through theentropy decoder 17010. For example, the entropy decoder 17010 may parsethe bitstream to derive information (e.g., video/image information)necessary for image reconstruction (or picture reconstruction). Forexample, the entropy decoder 17010 may decode the information in thebitstream based on a coding technique such as exponential Golomb coding,CAVLC, or CABAC, output values of syntax elements required for imagereconstruction, and quantized values of transform coefficients for theresidual. More specifically, in the CABAC entropy decoding, a bincorresponding to each syntax element in the bitstream may be received,and a context model may be determined based on decoding target syntaxelement information and decoding information about neighboring anddecoding target blocks or information about a symbol/bin decoded in aprevious step. Then, the probability of occurrence of a bin may bepredicted according to the determined context model, and arithmeticdecoding of the bin may be performed to generate a symbol correspondingto the value of each syntax element. According to the CABAC entropydecoding, after a context model is determined, the context model may beupdated based on the information about the symbol/bin decoded for thecontext model of the next symbol/bin. Information about the predictionin the information decoded by the entropy decoder 17010 may be providedto the predictors (the inter-predictor 17070 and the intra-predictor17080), and the residual values on which entropy decoding has beenperformed by the entropy decoder 17010, that is, the quantized transformcoefficients and related parameter information, may be input to theinverse quantizer 17020. In addition, information about filtering of theinformation decoded by the entropy decoder 17010 may be provided to thefilter 17050. A receiver (not shown) configured to receive a signaloutput from the encoder may be further configured as aninternal/external element of the decoder 17000. Alternatively, thereceiver may be a component of the entropy decoder 17010.

The inverse quantizer 17020 may output transform coefficients byinversely quantizing the quantized transform coefficients. The inversequantizer 17020 may rearrange the quantized transform coefficients inthe form of a two-dimensional block. In this case, the rearrangement maybe performed based on the coefficient scan order implemented by theencoder. The inverse quantizer 17020 may perform inverse quantization onthe quantized transform coefficients using a quantization parameter(e.g., quantization step size information), and acquire transformcoefficients.

The inverse transformer 17030 acquires a residual signal (residual blockand residual sample array) by inversely transforming the transformcoefficients.

The predictor may perform prediction on the current block and generate apredicted block including prediction samples for the current block. Thepredictor may determine whether intra-prediction or inter-prediction isto be applied to the current block based on the information about theprediction output from the entropy decoder 17010, and may determine aspecific intra-/inter-prediction mode.

The intra-predictor 265 may predict the current block with reference tothe samples in the current picture. The samples may be positioned in theneighbor of or away from the current block depending on the predictionmode. In intra-prediction, the prediction modes may include a pluralityof non-directional modes and a plurality of directional modes. Theintra-predictor 17080 may determine a prediction mode to be applied tothe current block, using the prediction mode applied to the neighboringblock.

The inter-predictor 17070 may derive a predicted block for the currentblock based on a reference block (reference sample array) specified by amotion vector on the reference picture. In this case, in order to reducethe amount of motion information transmitted in the inter-predictionmode, the motion information may be predicted on a per block, subblock,or sample basis based on the correlation in motion information betweenthe neighboring blocks and the current block. The motion information mayinclude a motion vector and a reference picture index. The motioninformation may further include information about an inter-predictiondirection (L0 prediction, L1 prediction, Bi prediction, etc.). In thecase of inter-prediction, the neighboring blocks may include a spatialneighboring block, which is present in the current picture, and atemporal neighboring block, which is present in the reference picture.For example, the inter-predictor 17070 may configure a motioninformation candidate list based on neighboring blocks and derive amotion vector of the current block and/or a reference picture indexbased on the received candidate selection information. Inter-predictionmay be performed based on various prediction modes. The informationabout the prediction may include information indicating aninter-prediction mode for the current block.

The adder 17040 may add the acquired residual signal to the predictionsignal (predicted block or prediction sample array) output from theinter-predictor 17070 or the intra-predictor 17080, thereby generating areconstructed signal (a reconstructed picture, a reconstructed block, ora reconstructed sample array). When there is no residual signal for aprocessing target block as in the case where the skip mode is applied,the predicted block may be used as the reconstructed block.

The adder 17040 may be called a reconstructor or a reconstructed blockgenerator. The generated reconstructed signal may be used forintra-prediction of the next processing target block in the currentpicture, or may be used for inter-prediction of the next picture throughfiltering as described below.

The filter 17050 may improve subjective/objective image quality byapplying filtering to the reconstructed signal. For example, the filter17050 may generate a modified reconstructed picture by applying variousfiltering techniques to the reconstructed picture, and may transmit themodified reconstructed picture to the memory 250, specifically, the DPBof the memory 17060. The various filtering techniques may include, forexample, deblocking filtering, sample adaptive offset, adaptive loopfiltering, and bilateral filtering.

The reconstructed picture stored in the DPB of the memory 17060 may beused as a reference picture in the inter-predictor 17070. The memory17060 may store the motion information about a block from which themotion information is derived (or decoded) in the current picture and/orthe motion information about the blocks in a picture that has alreadybeen reconstructed. The stored motion information may be delivered tothe inter-predictor 17070 so as to be used as the motion informationabout a spatial neighboring block or the motion information about atemporal neighboring block. The memory 17060 may store the reconstructedsamples of the reconstructed blocks in the current picture, and deliverthe reconstructed samples to the intra-predictor 17080.

In the present disclosure, the embodiments described regarding thefilter 160, the inter-predictor 180, and the intra-predictor 185 of theencoder 100 may be applied to the filter 17050, the inter-predictor17070 and the intra-predictor 17080 of the decoder 17000, respectively,in the same or corresponding manner.

At least one of the prediction, transform, and quantization proceduresdescribed above may be skipped. For example, for a block to which thepulse coding mode (PCM) is applied, the prediction, transform, andquantization procedures may be skipped, and the value of a decodedsample may be used as a sample of the reconstructed image.

Occupancy Map Decompression (16003)

This is a reverse process of the occupancy map compression describedabove. Occupancy map decompression is a process for reconstructing theoccupancy map by decompressing the occupancy map bitstream.

Auxiliary Patch Info Decompression (16004)

The auxiliary patch information may be reconstructed by performing thereverse process of the aforementioned auxiliary patch info compressionand decoding the compressed auxiliary patch info bitstream.

Geometry Reconstruction (16005)

This is a reverse process of the geometry image generation describedabove. Initially, a patch is extracted from the geometry image using thereconstructed occupancy map, the 2D position/size information about thepatch included in the auxiliary patch info, and the information aboutmapping between a block and the patch. Then, a point cloud isreconstructed in a 3D space based on the geometry image of the extractedpatch and the 3D position information about the patch included in theauxiliary patch info. When the geometry value corresponding to a point(u, v) within the patch is g(u, v), and the coordinates of the positionof the patch on the normal, tangent and bitangent axes of the 3D spaceare (δ0, s0, r0), ·δ(u, v), s(u, v), and r(u, v), which are the normal,tangent, and bitangent coordinates in the 3D space of a position mappedto point (u, v) may be expressed as follows:

δ(u,v)=δ0+g(u,v);

s(u,v)=s0+u;

r(u,v)=r0+v.

Smoothing (16006)

Smoothing, which is the same as the smoothing in the encoding processdescribed above, is a process for eliminating discontinuity that mayoccur on the patch boundary due to deterioration of the image qualityoccurring during the compression process.

Texture Reconstruction (16007)

Texture reconstruction is a process of reconstructing a color pointcloud by assigning color values to each point constituting a smoothedpoint cloud. It may be performed by assigning color values correspondingto a texture image pixel at the same position as in the geometry imagein the 2D space to points of a point of a point cloud corresponding tothe same position in the 3D space, based on the mapping informationabout the geometry image and the point cloud in the geometryreconstruction process described above.

Color Smoothing (16008)

Color smoothing is similar to the process of geometry smoothingdescribed above. Color smoothing is a process for eliminatingdiscontinuity that may occur on the patch boundary due to deteriorationof the image quality occurring during the compression process. Colorsmoothing may be performed through the following operations:

-   -   1) Calculate neighboring points of each point constituting the        reconstructed point cloud using the K-D tree or the like. The        neighboring point information calculated in the geometry        smoothing process described in section 2.5 may be used.    -   2) Determine whether each of the points is positioned on the        patch boundary. These operations may be performed based on the        boundary information calculated in the geometry smoothing        process described above.    -   3) Check the distribution of color values for the neighboring        points of the points present on the boundary and determine        whether smoothing is to be performed. For example, when the        entropy of luminance values is less than or equal to a threshold        local entry (there are many similar luminance values), it may be        determined that the corresponding portion is not an edge        portion, and smoothing may be performed. As a method of        smoothing, the color value of the point may be replaced with the        average of the color values of the neighboring points.

FIG. 18 is a flowchart illustrating operation of a transmission deviceaccording to embodiments of the present disclosure.

The transmission device according to the embodiments may correspond tothe transmission device of FIG. 1 , the encoding process of FIG. 4 , andthe 2D video/image encoder of FIG. 15 , or perform some/all of theoperations thereof. Each component of the transmission device maycorrespond to software, hardware, a processor and/or a combinationthereof.

An operation process of the transmission terminal for compression andtransmission of point cloud data using V-PCC may be performed asillustrated in the figure.

The point cloud data transmission device according to the embodimentsmay be referred to as a transmission device.

Regarding a patch generator 18000, a patch for 2D image mapping of apoint cloud is generated. Auxiliary patch information is generated as aresult of the patch generation. The generated information may be used inthe processes of geometry image generation, texture image generation,and geometry reconstruction for smoothing.

Regarding a patch packer 18001, a patch packing process of mapping thegenerated patches into the 2D image is performed. As a result of patchpacking, an occupancy map may be generated. The occupancy map may beused in the processes of geometry image generation, texture imagegeneration, and geometry reconstruction for smoothing.

A geometry image generator 18002 generates a geometry image based on theauxiliary patch information and the occupancy map. The generatedgeometry image is encoded into one bitstream through video encoding.

An encoding preprocessor 18003 may include an image padding procedure.The geometry image regenerated by decoding the generated geometry imageor the encoded geometry bitstream may be used for 3D geometryreconstruction and then be subjected to a smoothing process.

A texture image generator 18004 may generate a texture image based onthe (smoothed) 3D geometry, the point cloud, the auxiliary patchinformation, and the occupancy map. The generated texture image may beencoded into one video bitstream.

A metadata encoder 18005 may encode the auxiliary patch information intoone metadata bitstream.

A video encoder 18006 may encode the occupancy map into one videobitstream.

A multiplexer 18007 may multiplex the video bitstreams of the generatedgeometry image, texture image, and occupancy map and the metadatabitstream of the auxiliary patch information into one bitstream.

A transmitter 18008 may transmit the bitstream to the receptionterminal. Alternatively, the video bitstreams of the generated geometryimage, texture image, and the occupancy map and the metadata bitstreamof the auxiliary patch information may be processed into a file of oneor more track data or encapsulated into segments and may be transmittedto the reception terminal through the transmitter.

FIG. 19 is a flowchart illustrating operation of a reception deviceaccording to embodiments.

The reception device according to the embodiments may correspond to thereception device of FIG. 1 , the decoding process of FIG. 16 , and the2D video/image encoder of FIG. 17 , or perform some/all of theoperations thereof. Each component of the reception device maycorrespond to software, hardware, a processor and/or a combinationthereof.

The operation of the reception terminal for receiving and reconstructingpoint cloud data using V-PCC may be performed as illustrated in thefigure. The operation of the V-PCC reception terminal may follow thereverse process of the operation of the V-PCC transmission terminal ofFIG. 18 .

The point cloud data reception device according to the embodiments maybe referred to as a reception device.

The bitstream of the received point cloud is demultiplexed into thevideo bitstreams of the compressed geometry image, texture image,occupancy map and the metadata bitstream of the auxiliary patchinformation by a demultiplexer 19000 after file/segment decapsulation. Avideo decoder 19001 and a metadata decoder 19002 decode thedemultiplexed video bitstreams and metadata bitstream. 3D geometry isreconstructed by a geometry reconstructor 19003 based on the decodedgeometry image, occupancy map, and auxiliary patch information, and isthen subjected to a smoothing process performed by a smoother 19004. Acolor point cloud image/picture may be reconstructed by a texturereconstructor 19005 by assigning color values to the smoothed 3Dgeometry based on the texture image. Thereafter, a color smoothingprocess may be additionally performed to improve theobjective/subjective visual quality, and a modified point cloudimage/picture derived through the color smoothing process is shown tothe user through the rendering process (through, for example, the pointcloud renderer). In some cases, the color smoothing process may beskipped.

FIG. 20 illustrates an exemplary architecture for V-PCC based storageand streaming of point cloud data according to embodiments.

A part/the entirety of the system of FIG. 20 may include some or all ofthe transmission device and reception device of FIG. 1 , the encodingprocess of FIG. 4 , the 2D video/image encoder of FIG. 15 , the decodingprocess of FIG. 16 , the transmission device of FIG. 18 , and/or thereception device of FIG. 19 . Each component in the figure maycorrespond to software, hardware, a processor and/or a combinationthereof.

FIGS. 20 to 22 are diagrams illustrating a structure in which a systemis additionally connected to the transmission device and the receptiondevice according to embodiments. The transmission device and thereception device the system according to embodiments may be referred toas a transmission/reception apparatus according to the embodiments.

In the apparatus according to the embodiments illustrated in FIGS. 20 to22 , the transmitting device corresponding to FIG. 18 or the like maygenerate a container suitable for a data format for transmission of abitstream containing encoded point cloud data.

The V-PCC system according to the embodiments may create a containerincluding point cloud data, and may further add additional datanecessary for efficient transmission/reception to the container.

The reception device according to the embodiments may receive and parsethe container based on the system shown in FIGS. 20 to 22 . Thereception device corresponding to FIG. 19 or the like may decode andrestore point cloud data from the parsed bitstream.

The figure shows the overall architecture for storing or streaming pointcloud data compressed based on video-based point cloud compression(V-PCC). The process of storing and streaming the point cloud data mayinclude an acquisition process, an encoding process, a transmissionprocess, a decoding process, a rendering process, and/or a feedbackprocess.

The embodiments propose a method of effectively providing point cloudmedia/content/data.

In order to effectively provide point cloud media/content/data, a pointcloud acquirer 20000 may acquire a point cloud video. For example, oneor more cameras may acquire point cloud data through capture,composition or generation of a point cloud. Through this acquisitionprocess, a point cloud video including a 3D position (which may berepresented by x, y, and z position values, etc.) (hereinafter referredto as geometry) of each point and attributes (color, reflectance,transparency, etc.) of each point may be acquired. For example, aPolygon File format (PLY) (or Stanford Triangle format) file or the likecontaining the point cloud video may be generated. For point cloud datahaving multiple frames, one or more files may be acquired. In thisprocess, point cloud related metadata (e.g., metadata related tocapture, etc.) may be generated.

Post-processing for improving the quality of the content may be neededfor the captured point cloud video. In the video capture process, themaximum/minimum depth may be adjusted within the range provided by thecamera equipment. Even after the adjustment, point data of an unwantedarea may still be present. Accordingly, post-processing of removing theunwanted area (e.g., the background) or recognizing a connected spaceand filling the spatial holes may be performed. In addition, pointclouds extracted from the cameras sharing a spatial coordinate systemmay be integrated into one piece of content through the process oftransforming each point into a global coordinate system based on thecoordinates of the location of each camera acquired through acalibration process. Thereby, a point cloud video with a high density ofpoints may be acquired.

A point cloud pre-processor 20001 may generate one or morepictures/frames of the point cloud video. Here, a picture/frame maygenerally represent a unit representing one image in a specific timeinterval. When points constituting the point cloud video is divided intoone or more patches (sets of points that constitute the point cloudvideo, wherein the points belonging to the same patch are adjacent toeach other in the 3D space and are mapped in the same direction amongthe planar faces of a 6-face bounding box when mapped to a 2D image) andmapped to a 2D plane, an occupancy map picture/frame of a binary map,which indicates presence or absence of data at the correspondingposition in the 2D plane with a value of 0 or 1 may be generated. Inaddition, a geometry picture/frame, which is in the form of a depth mapthat represents the information about the position (geometry) of eachpoint constituting the point cloud video on a patch-by-patch basis, maybe generated. A texture picture/frame, which represents the colorinformation about each point constituting the point cloud video on apatch-by-patch basis, may be generated. In this process, metadata neededto reconstruct the point cloud from the individual patches may begenerated. The metadata may include information about the patches, suchas the position and size of each patch in the 2D/3D space. Thesepictures/frames may be generated continuously in temporal order toconstruct a video stream or metadata stream.

A point cloud video encoder 20002 may encode one or more video streamsrelated to a point cloud video. One video may include multiple frames,and one frame may correspond to a still image/picture. In the presentdisclosure, the point cloud video may include a point cloudimage/frame/picture, and the term “point cloud video” may be usedinterchangeably with the point cloud video/frame/picture. The pointcloud video encoder may perform a video-based point cloud compression(V-PCC) procedure. The point cloud video encoder may perform a series ofprocedures such as prediction, transform, quantization, and entropycoding for compression and coding efficiency. The encoded data (encodedvideo/image information) may be output in the form of a bitstream. Basedon the V-PCC procedure, the point cloud video encoder may encode pointcloud video by dividing the same into a geometry video, an attributevideo, an occupancy map video, and metadata, for example, informationabout patches, as described below. The geometry video may include ageometry image, the attribute video may include an attribute image, andthe occupancy map video may include an occupancy map image. The patchdata, which is auxiliary information, may include patch relatedinformation. The attribute video/image may include a texturevideo/image.

A point cloud image encoder 20003 may encode one or more images relatedto a point cloud video. The point cloud image encoder may perform avideo-based point cloud compression (V-PCC) procedure. The point cloudimage encoder may perform a series of procedures such as prediction,transform, quantization, and entropy coding for compression and codingefficiency. The encoded image may be output in the form of a bitstream.Based on the V-PCC procedure, the point cloud image encoder may encodethe point cloud image by dividing the same into a geometry image, anattribute image, an occupancy map image, and metadata, for example,information about patches, as described below.

The point cloud video encoder and/or the point cloud image encoderaccording to the embodiments may generate a PCC bitstream (G-PCC and/orV-PCC bitstream) according to the embodiments.

According to embodiments, the video encoder 2002, the image encoder20002, the video decoding 20006, and the image decoding may be performedby one encoder/decoder as described above, and may be performed alongseparate paths as shown in the figure.

In file/segment encapsulation 20004, the encoded point cloud data and/orpoint cloud-related metadata may be encapsulated into a file or asegment for streaming. Here, the point cloud-related metadata may bereceived from the metadata processor or the like. The metadata processormay be included in the point cloud video/image encoder or may beconfigured as a separate component/module. The encapsulation processormay encapsulate the corresponding video/image/metadata in a file formatsuch as ISOBMFF or in the form of a DASH segment or the like. Accordingto an embodiment, the encapsulation processor may include the pointcloud metadata in the file format. The point cloud-related metadata maybe included, for example, in boxes at various levels on the ISOBMFF fileformat or as data in a separate track within the file. According to anembodiment, the encapsulation processor may encapsulate the pointcloud-related metadata into a file.

The encapsulation or encapsulator according to the embodiments maydivide the G-PCC/V-PCC bitstream into one or multiple tracks and storethe same in a file, and may also encapsulate signaling information forthis operation. In addition, the atlas stream included on theG-PCC/V-PCC bitstream may be stored as a track in the file, and relatedsignaling information may be stored. Furthermore, an SEI message presentin the G-PCC/V-PCC bitstream may be stored in a track in the file andrelated signaling information may be stored.

A transmission processor may perform processing of the encapsulatedpoint cloud data for transmission according to the file format. Thetransmission processor may be included in the transmitter or may beconfigured as a separate component/module. The transmission processormay process the point cloud data according to a transmission protocol.The processing for transmission may include processing for delivery overa broadcast network and processing for delivery through a broadband.According to an embodiment, the transmission processor may receive pointcloud-related metadata from the metadata processor as well as the pointcloud data, and perform processing of the point cloud video data fortransmission.

The transmitter may transmit a point cloud bitstream or a file/segmentincluding the bitstream to the receiver of the reception device over adigital storage medium or a network. For transmission, processingaccording to any transmission protocol may be performed. The dataprocessed for transmission may be delivered over a broadcast networkand/or through a broadband. The data may be delivered to the receptionside in an on-demand manner. The digital storage medium may includevarious storage media such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD.The transmitter may include an element for generating a media file in apredetermined file format, and may include an element for transmissionover a broadcast/communication network. The receiver may extract thebitstream and transmit the extracted bitstream to the decoder.

The receiver may receive point cloud data transmitted by the point clouddata transmission device according to the present disclosure. Dependingon the transmission channel, the receiver may receive the point clouddata over a broadcast network or through a broadband. Alternatively, thepoint cloud data may be received through the digital storage medium. Thereceiver may include a process of decoding the received data andrendering the data according to the viewport of the user.

The reception processor may perform processing on the received pointcloud video data according to the transmission protocol. The receptionprocessor may be included in the receiver or may be configured as aseparate component/module. The reception processor may reversely performthe process of the transmission processor above described so as tocorrespond to the processing for transmission performed at thetransmission side. The reception processor may deliver the acquiredpoint cloud video to a decapsulation processor, and the acquired pointcloud-related metadata to a metadata parser.

A decapsulation processor (file/segment decapsulation) 20005 maydecapsulate the point cloud data received in the form of a file from thereception processor. The decapsulation processor may decapsulate filesaccording to ISOBMFF or the like, and may acquire a point cloudbitstream or point cloud-related metadata (or a separate metadatabitstream). The acquired point cloud bitstream may be delivered to thepoint cloud decoder, and the acquired point cloud video-related metadata(metadata bitstream) may be delivered to the metadata processor. Thepoint cloud bitstream may include the metadata (metadata bitstream). Themetadata processor may be included in the point cloud decoder or may beconfigured as a separate component/module. The point cloud video-relatedmetadata acquired by the decapsulation processor may take the form of abox or track in the file format. The decapsulation processor may receivemetadata necessary for decapsulation from the metadata processor, whennecessary. The point cloud-related metadata may be delivered to thepoint cloud decoder and used in a point cloud decoding procedure, or maybe transferred to the renderer and used in a point cloud renderingprocedure.

The point cloud video decoder 20006 may receive the bitstream and decodethe video/image by performing an operation corresponding to theoperation of the point cloud video encoder. In this case, the pointcloud video decoder may decode the point cloud video by dividing thesame into a geometry video, an attribute video, an occupancy map video,and auxiliary patch information as described below. The geometry videomay include a geometry image, the attribute video may include anattribute image, and the occupancy map video may include an occupancymap image. The auxiliary information may include auxiliary patchinformation. The attribute video/image may include a texturevideo/image.

The 3D geometry may be reconstructed based on the decoded geometryimage, the occupancy map, and auxiliary patch information, and then maybe subjected to a smoothing process. The color point cloud image/picturemay be reconstructed by assigning a color value to the smoothed 3Dgeometry based on the texture image. The renderer may render thereconstructed geometry and the color point cloud image/picture. Therendered video/image may be displayed through the display. All or partof the rendered result may be shown to the user through a VR/AR displayor a typical display.

A sensor/tracker (sensing/tracking) 20007 acquires orientationinformation and/or user viewport information from the user or thereception side and delivers the orientation information and/or the userviewport information to the receiver and/or the transmitter. Theorientation information may represent information about the position,angle, movement, etc. of the user's head, or represent information aboutthe position, angle, movement, etc. of a device through which the useris viewing a video/image. Based on this information, information aboutthe area currently viewed by the user in a 3D space, that is, viewportinformation may be calculated.

The viewport information may be information about an area in a 3D spacecurrently viewed by the user through a device or an HMD. A device suchas a display may extract a viewport area based on the orientationinformation, a vertical or horizontal FOV supported by the device, andthe like. The orientation or viewport information may be extracted orcalculated at the reception side. The orientation or viewportinformation analyzed at the reception side may be transmitted to thetransmission side on a feedback channel.

Based on the orientation information acquired by the sensor/trackerand/or the viewport information indicating the area currently viewed bythe user, the receiver may efficiently extract or decode only media dataof a specific area, i.e., the area indicated by the orientationinformation and/or the viewport information from the file. In addition,based on the orientation information and/or viewport informationacquired by the sensor/tracker, the transmitter may efficiently encodeonly the media data of the specific area, that is, the area indicated bythe orientation information and/or the viewport information, or generateand transmit a file therefor.

The renderer may render the decoded point cloud data in a 3D space. Therendered video/image may be displayed through the display. The user mayview all or part of the rendered result through a VR/AR display or atypical display.

The feedback process may include transferring various feedbackinformation that may be acquired in the rendering/displaying process tothe transmitting side or the decoder of the receiving side. Through thefeedback process, interactivity may be provided in consumption of pointcloud data. According to an embodiment, head orientation information,viewport information indicating an area currently viewed by a user, andthe like may be delivered to the transmitting side in the feedbackprocess. According to an embodiment, the user may interact with what isimplemented in the VR/AR/MR/autonomous driving environment. In thiscase, information related to the interaction may be delivered to thetransmitting side or a service provider in the feedback process.According to an embodiment, the feedback process may be skipped.

According to an embodiment, the above-described feedback information maynot only be transmitted to the transmitting side, but also be consumedat the receiving side. That is, the decapsulation processing, decoding,and rendering processes at the receiving side may be performed based onthe above-described feedback information. For example, the point clouddata about the area currently viewed by the user may be preferentiallydecapsulated, decoded, and rendered based on the orientation informationand/or the viewport information.

A method of transmitting point cloud data according to embodiments mayinclude encoding point cloud data, encapsulating the point cloud data,and transmitting the point cloud data.

A method of receiving point cloud data according to embodiments mayinclude receiving point cloud data, decapsulating the point cloud data,and decoding the point cloud data.

FIG. 21 is an exemplary block diagram of an device for storing andtransmitting point cloud data according to embodiments.

FIG. 21 shows a point cloud system according to embodiments. A part/theentirety of the system may include some or all of the transmissiondevice and reception device of FIG. 1 , the encoding process of FIG. 4 ,the 2D video/image encoder of FIG. 15 , the decoding process of FIG. 16, the transmission device of FIG. 18 , and/or the reception device ofFIG. 19 . In addition, it may be included or corresponded to a part/theentirety of the system of FIG. 20 .

A point cloud data transmission device according to embodiments may beconfigured as shown in the figure. Each element of the transmissiondevice may be a module/unit/component/hardware/software/a processor.

The geometry, attribute, auxiliary data, and mesh data of the pointcloud may each be configured as a separate stream or stored in differenttracks in a file. Furthermore, they may be included in a separatesegment.

A point cloud acquirer (point cloud acquisition) 21000 acquires a pointcloud. For example, one or more cameras may acquire point cloud datathrough capture, composition or generation of a point cloud. Throughthis acquisition process, point cloud data including a 3D position(which may be represented by x, y, and z position values, etc.)(hereinafter referred to as geometry) of each point and attributes(color, reflectance, transparency, etc.) of each point may be acquired.For example, a Polygon File format (PLY) (or Stanford Triangle format)file or the like including the point cloud data may be generated. Forpoint cloud data having multiple frames, one or more files may beacquired. In this process, point cloud related metadata (e.g., metadatarelated to capture, etc.) may be generated.

A patch generator (or patch generation) 21002 generates patches from thepoint cloud data. The patch generator generates point cloud data orpoint cloud video as one or more pictures/frames. A picture/frame maygenerally represent a unit representing one image in a specific timeinterval. When points constituting the point cloud video is divided intoone or more patches (sets of points that constitute the point cloudvideo, wherein the points belonging to the same patch are adjacent toeach other in the 3D space and are mapped in the same direction amongthe planar faces of a 6-face bounding box when mapped to a 2D image) andmapped to a 2D plane, an occupancy map picture/frame in a binary map,which indicates presence or absence of data at the correspondingposition in the 2D plane with 0 or 1 may be generated. In addition, ageometry picture/frame, which is in the form of a depth map thatrepresents the information about the position (geometry) of each pointconstituting the point cloud video on a patch-by-patch basis, may begenerated. A texture picture/frame, which represents the colorinformation about each point constituting the point cloud video on apatch-by-patch basis, may be generated. In this process, metadata neededto reconstruct the point cloud from the individual patches may begenerated. The metadata may include information about the patches, suchas the position and size of each patch in the 2D/3D space. Thesepictures/frames may be generated continuously in temporal order toconstruct a video stream or metadata stream.

In addition, the patches may be used for 2D image mapping. For example,the point cloud data may be projected onto each face of a cube. Afterpatch generation, a geometry image, one or more attribute images, anoccupancy map, auxiliary data, and/or mesh data may be generated basedon the generated patches.

Geometry image generation, attribute image generation, occupancy mapgeneration, auxiliary data generation, and/or mesh data generation areperformed by a pre-processor or a controller.

In geometry image generation 21002, a geometry image is generated basedon the result of the patch generation. Geometry represents a point in a3D space. The geometry image is generated using the occupancy map, whichincludes information related to 2D image packing of the patches,auxiliary data (patch data), and/or mesh data based on the patches. Thegeometry image is related to information such as a depth (e.g., near,far) of the patch generated after the patch generation.

In attribute image generation 21003, an attribute image is generated.For example, an attribute may represent a texture. The texture may be acolor value that matches each point. According to embodiments, images ofa plurality of attributes (such as color and reflectance) (N attributes)including a texture may be generated. The plurality of attributes mayinclude material information and reflectance. According to anembodiment, the attributes may additionally include informationindicating a color, which may vary depending on viewing angle and lighteven for the same texture.

In occupancy map generation 21004, an occupancy map is generated fromthe patches. The occupancy map includes information indicating presenceor absence of data in the pixel, such as the corresponding geometry orattribute image.

In auxiliary data generation 21005, auxiliary data including informationabout the patches is generated. That is, the auxiliary data representsmetadata about a patch of a point cloud object. For example, it mayrepresent information such as normal vectors for the patches.Specifically, the auxiliary data may include information needed toreconstruct the point cloud from the patches (e.g., information aboutthe positions, sizes, and the like of the patches in 2D/3D space, andprojection (normal) plane identification information, patch mappinginformation, etc.)

In mesh data generation 21006, mesh data is generated from the patches.Mesh represents connection between neighboring points. For example, itmay represent data of a triangular shape. For example, the mesh datarefers to connectivity between the points.

A point cloud pre-processor or controller generates metadata related topatch generation, geometry image generation, attribute image generation,occupancy map generation, auxiliary data generation, and mesh datageneration.

The point cloud transmission device performs video encoding and/or imageencoding in response to the result generated by the pre-processor. Thepoint cloud transmission device may generate point cloud image data aswell as point cloud video data. According to embodiments, the pointcloud data may have only video data, only image data, and/or both videodata and image data.

A video encoder 21007 performs geometry video compression, attributevideo compression, occupancy map compression, auxiliary datacompression, and/or mesh data compression. The video encoder generatesvideo stream(s) containing encoded video data.

Specifically, in the geometry video compression, point cloud geometryvideo data is encoded. In the attribute video compression, attributevideo data of the point cloud is encoded. In the auxiliary datacompression, auxiliary data associated with the point cloud video datais encoded. In the mesh data compression, mesh data of the point cloudvideo data is encoded. The respective operations of the point cloudvideo encoder may be performed in parallel.

An image encoder 21008 performs geometry image compression, attributeimage compression, occupancy map compression, auxiliary datacompression, and/or mesh data compression. The image encoder generatesimage(s) containing encoded image data.

Specifically, in the geometry image compression, the point cloudgeometry image data is encoded. In the attribute image compression, theattribute image data of the point cloud is encoded. In the auxiliarydata compression, the auxiliary data associated with the point cloudimage data is encoded. In the mesh data compression, the mesh dataassociated with the point cloud image data is encoded. The respectiveoperations of the point cloud image encoder may be performed inparallel.

The video encoder and/or the image encoder may receive metadata from thepre-processor. The video encoder and/or the image encoder may performeach encoding process based on the metadata.

A file/segment encapsulator (file/segment encapsulation) 21009encapsulates the video stream(s) and/or image(s) in the form of a fileand/or segment. The file/segment encapsulator performs video trackencapsulation, metadata track encapsulation, and/or image encapsulation.

In the video track encapsulation, one or more video streams may beencapsulated into one or more tracks.

In the metadata track encapsulation, metadata related to a video streamand/or an image may be encapsulated in one or more tracks. The metadataincludes data related to the content of the point cloud data. Forexample, it may include initial viewing orientation metadata. Accordingto embodiments, the metadata may be encapsulated into a metadata track,or may be encapsulated together in a video track or an image track.

In the image encapsulation, one or more images may be encapsulated intoone or more tracks or items.

For example, according to embodiments, when four video streams and twoimages are input to the encapsulator, the four video streams and twoimages may be encapsulated in one file.

The point cloud video encoder and/or the point cloud image encoderaccording to the embodiments may generate a G-PCC/V-PCC bitstreamaccording to the embodiments.

The file/segment encapsulator may receive metadata from thepre-processor. The file/segment encapsulator may perform encapsulationbased on the metadata.

A file and/or a segment generated by the file/segment encapsulation aretransmitted by the point cloud transmission device or the transmitter.For example, the segment(s) may be delivered based on a DASH-basedprotocol.

The encapsulation or encapsulator according to the embodiments maydivide the V-PCC bitstream into one or multiple tracks and store thesame in a file, and may also encapsulate signaling information for thisoperation. In addition, the atlas stream included on the V-PCC bitstreammay be stored as a track in the file, and related signaling informationmay be stored. Furthermore, an SEI message present in the V-PCCbitstream may be stored in a track in the file and related signalinginformation may be stored.

The transmitter may transmit a point cloud bitstream or a file/segmentincluding the bitstream to the receiver of the reception device over adigital storage medium or a network. Processing according to anytransmission protocol may be performed for transmission. The data thathas been processed for transmission may be delivered over a broadcastnetwork and/or through a broadband. The data may be delivered to thereceiving side in an on-demand manner. The digital storage medium mayinclude various storage media such as USB, SD, CD, DVD, Blu-ray, HDD,and SSD. The deliverer may include an element for generating a mediafile in a predetermined file format, and may include an element fortransmission over a broadcast/communication network. The delivererreceives orientation information and/or viewport information from thereceiver. The deliverer may deliver the acquired orientation informationand/or viewport information (or information selected by the user) to thepre-processor, the video encoder, the image encoder, the file/segmentencapsulator, and/or the point cloud encoder. Based on the orientationinformation and/or the viewport information, the point cloud encoder mayencode all point cloud data or the point cloud data indicated by theorientation information and/or the viewport information. Based on theorientation information and/or the viewport information, thefile/segment encapsulator may encapsulate all point cloud data or thepoint cloud data indicated by the orientation information and/or theviewport information. Based on the orientation information and/or theviewport information, the deliverer may deliver all point cloud data orthe point cloud data indicated by the orientation information and/or theviewport information.

For example, the pre-processor may perform the above-described operationon all the point cloud data or on the point cloud data indicated by theorientation information and/or the viewport information. The videoencoder and/or the image encoder may perform the above-describedoperation on all the point cloud data or on the point cloud dataindicated by the orientation information and/or the viewportinformation. The file/segment encapsulator may perform theabove-described operation on all the point cloud data or on the pointcloud data indicated by the orientation information and/or the viewportinformation. The transmitter may perform the above-described operationon all the point cloud data or on the point cloud data indicated by theorientation information and/or the viewport information.

FIG. 22 is an exemplary block diagram of a point cloud data receptiondevice according to embodiments.

FIG. 22 shows a point cloud system according to embodiments. A part/theentirety of the system may include some or all of the transmissiondevice and reception device of FIG. 1 , the encoding process of FIG. 4 ,the 2D video/image encoder of FIG. 15 , the decoding process of FIG. 16, the transmission device of FIG. 18 , and/or the reception device ofFIG. 19 . In addition, it may be included or corresponded to a part/theentirety of the system of FIGS. 20 and 21 .

Each component of the reception device may be amodule/unit/component/hardware/software/processor. A delivery client mayreceive point cloud data, a point cloud bitstream, or a file/segmentincluding the bitstream transmitted by the point cloud data transmissiondevice according to the embodiments. The receiver may receive the pointcloud data over a broadcast network or through a broadband depending onthe channel used for the transmission. Alternatively, the point cloudvideo data may be received through a digital storage medium. Thereceiver may include a process of decoding the received data andrendering the received data according to the user viewport. Thereception processor may perform processing on the received point clouddata according to a transmission protocol. A reception processor may beincluded in the receiver or configured as a separate component/module.The reception processor may reversely perform the process of thetransmission processor described above so as to correspond to theprocessing for transmission performed at the transmitting side. Thereception processor may deliver the acquired point cloud data to thedecapsulation processor and the acquired point cloud related metadata tothe metadata parser.

The sensor/tracker (sensing/tracking) acquires orientation informationand/or viewport information. The sensor/tracker may deliver the acquiredorientation information and/or viewport information to the deliveryclient, the file/segment decapsulator, and the point cloud decoder.

The delivery client may receive all point cloud data or the point clouddata indicated by the orientation information and/or the viewportinformation based on the orientation information and/or the viewportinformation. The file/segment decapsulator may decapsulate all pointcloud data or the point cloud data indicated by the orientationinformation and/or the viewport information based on the orientationinformation and/or the viewport information. The point cloud decoder(the video decoder and/or the image decoder) may decode all point clouddata or the point cloud data indicated by the orientation informationand/or the viewport information based on the orientation informationand/or the viewport information. The point cloud processor may processall point cloud data or the point cloud data indicated by theorientation information and/or the viewport information based on theorientation information and/or the viewport information.

A file/segment decapsulator (file/segment decapsulation) 22000 performsvideo track decapsulation, metadata track decapsulation, and/or imagedecapsulation. The decapsulation processor (file/segment decapsulation)may decapsulate the point cloud data in the form of a file received fromthe reception processor. The decapsulation processor (file/segmentdecapsulation) may decapsulate files or segments according to ISOBMFF,etc., to acquire a point cloud bitstream or point cloud-related metadata(or a separate metadata bitstream). The acquired point cloud bitstreammay be delivered to the point cloud decoder, and the acquired pointcloud-related metadata (or metadata bitstream) may be delivered to themetadata processor. The point cloud bitstream may include the metadata(metadata bitstream). The metadata processor may be included in thepoint cloud video decoder or may be configured as a separatecomponent/module. The point cloud-related metadata acquired by thedecapsulation processor may take the form of a box or track in a fileformat. The decapsulation processor may receive metadata necessary fordecapsulation from the metadata processor, when necessary. The pointcloud-related metadata may be delivered to the point cloud decoder andused in a point cloud decoding procedure, or may be delivered to therenderer and used in a point cloud rendering procedure. The file/segmentdecapsulator may generate metadata related to the point cloud data.

In the video track decapsulation, a video track contained in the fileand/or segment is decapsulated. Video stream(s) including a geometryvideo, an attribute video, an occupancy map, auxiliary data, and/or meshdata are decapsulated.

In the metadata track decapsulation, a bitstream containing metadatarelated to the point cloud data and/or auxiliary data is decapsulated.

In the image decapsulation, image(s) including a geometry image, anattribute image, an occupancy map, auxiliary data and/or mesh data aredecapsulated.

The decapsulation or decapsulator according to the embodiments maydivide and parse (decapsulate) the G-PCC/V-PCC bitstream based on one ormore tracks in a file, and may also decapsulate signaling informationtherefor. In addition, the atlas stream included in the G-PCC/V-PCCbitstream may be decapsulated based on a track in the file, and relatedsignaling information may be parsed. Furthermore, an SEI message presentin the G-PCC/V-PCC bitstream may be decapsulated based on a track in thefile, and related signaling information may be also acquired.

The video decoding or video decoder 22001 performs geometry videodecompression, attribute video decompression, occupancy mapdecompression, auxiliary data decompression, and/or mesh datadecompression. The video decoder decodes the geometry video, theattribute video, the auxiliary data, and/or the mesh data in a processcorresponding to the process performed by the video encoder of the pointcloud transmission device according to the embodiments.

The image decoding or image decoder 22002 performs geometry imagedecompression, attribute image decompression, occupancy mapdecompression, auxiliary data decompression, and/or mesh datadecompression. The image decoder decodes the geometry image, theattribute image, the auxiliary data, and/or the mesh data in a processcorresponding to the process performed by the image encoder of the pointcloud transmission device according to the embodiments.

The video decoding and the image decoding according to the embodimentsmay be processed by one video/image decoder as described above, and maybe performed along separate paths as illustrated in the figure.

The video decoding and/or the image decoding may generate metadatarelated to the video data and/or the image data.

The point cloud video encoder and/or the point cloud image encoderaccording to the embodiments may decode the G-PCC/V-PCC bitstreamaccording to the embodiments.

In point cloud processing 22003, geometry reconstruction and/orattribute reconstruction are performed.

In the geometry reconstruction, the geometry video and/or geometry imageare reconstructed from the decoded video data and/or decoded image databased on the occupancy map, auxiliary data and/or mesh data.

In the attribute reconstruction, the attribute video and/or theattribute image are reconstructed from the decoded attribute videoand/or the decoded attribute image based on the occupancy map, auxiliarydata, and/or mesh data. According to embodiments, for example, theattribute may be a texture. According to embodiments, an attribute mayrepresent a plurality of pieces of attribute information. When there isa plurality of attributes, the point cloud processor according to theembodiments performs a plurality of attribute reconstructions.

The point cloud processor may receive metadata from the video decoder,the image decoder, and/or the file/segment decapsulator, and process thepoint cloud based on the metadata.

The point cloud rendering or point cloud renderer renders thereconstructed point cloud. The point cloud renderer may receive metadatafrom the video decoder, the image decoder, and/or the file/segmentdecapsulator, and render the point cloud based on the metadata.

The display actually displays the result of rendering on the display.

As shown in FIGS. 15 to 19 , after encoding/decoding, the method/deviceaccording to the embodiments the point cloud data as shown in 15 to 19,the bitstream containing the point cloud data may be encapsulated and/ordecapsulated in the form of a file and/or a segment.

For example, a point cloud data device according to the embodiments mayencapsulate point cloud data based on a file. The file may include aV-PCC track containing parameters for a point cloud, a geometry trackcontaining geometry, an attribute track containing an attribute, and anoccupancy track containing an occupancy map.

In addition, a point cloud data reception device according toembodiments decapsulates the point cloud data based on a file. The filemay include a V-PCC track containing parameters for a point cloud, ageometry track containing geometry, an attribute track containing anattribute, and an occupancy track containing an occupancy map.

The operation described above may be performed by the file/segmentencapsulator 20004, 20005 of FIG. 20 , the file/segment encapsulator21009 of FIG. 21 , and the file/segment encapsulator 22000 of FIG. 22 .

FIG. 23 illustrates an exemplary structure operable in connection withpoint cloud data transmission/reception methods/devices according toembodiments.

In the structure according to the embodiments, at least one of a server2360, a robot 2310, a self-driving vehicle 2320, an XR device 2330, asmartphone 2340, a home appliance 2350 and/or a head-mount display (HMD)2370 is connected to a cloud network 2300. Here, the robot 2310, theself-driving vehicle 2320, the XR device 2330, the smartphone 2340, orthe home appliance 2350 may be referred to as a device. In addition, theXR device 1730 may correspond to a point cloud data (PCC) deviceaccording to embodiments or may be operatively connected to the PCCdevice.

The cloud network 2300 may represent a network that constitutes part ofthe cloud computing infrastructure or is present in the cloud computinginfrastructure. Here, the cloud network 2300 may be configured using a3G network, 4G or Long Term Evolution (LTE) network, or a 5G network.

The server 2360 may be connected to at least one of the robot 2310, theself-driving vehicle 2320, the XR device 2330, the smartphone 2340, thehome appliance 2350, and/or the HMD 2370 over the cloud network 2300 andmay assist at least a part of the processing of the connected devices2310 to 2370.

The HMD 2370 represents one of the implementation types of the XR deviceand/or the PCC device according to the embodiments. An HMD type deviceaccording to embodiments includes a communication unit, a control unit,a memory, an I/O unit, a sensor unit, and a power supply unit.

Hereinafter, various embodiments of the devices 2310 to 2350 to whichthe above-described technology is applied will be described. The devices2310 to 2350 illustrated in FIG. 23 may be operatively connected/coupledto a point cloud data transmission and reception device according to theabove-described embodiments.

<PCC+XR>

The XR/PCC device 2330 may employ PCC technology and/or XR (AR+VR)technology, and may be implemented as an HMD, a head-up display (HUD)provided in a vehicle, a television, a mobile phone, a smartphone, acomputer, a wearable device, a home appliance, a digital signage, avehicle, a stationary robot, or a mobile robot.

The XR/PCC device 2330 may analyze 3D point cloud data or image dataacquired through various sensors or from an external device and generateposition data and attribute data about 3D points. Thereby, the XR/PCCdevice 2330 may acquire information about the surrounding space or areal object, and render and output an XR object. For example, the XR/PCCdevice 2330 may match an XR object including auxiliary information abouta recognized object with the recognized object and output the matched XRobject.

<PCC+XR+Mobile Phone>

The XR/PCC device 2330 may be implemented as a mobile phone 2340 byapplying PCC technology.

The mobile phone 2340 may decode and display point cloud content basedon the PCC technology.

<PCC+Self-Driving+XR>

The self-driving vehicle 2320 may be implemented as a mobile robot, avehicle, an unmanned aerial vehicle, or the like by applying the PCCtechnology and the XR technology.

The self-driving vehicle 2320 to which the XR/PCC technology is appliedmay represent an autonomous vehicle provided with means for providing anXR image, or an autonomous vehicle that is a target ofcontrol/interaction in the XR image. In particular, the self-drivingvehicle 2320, which is a target of control/interaction in the XR image,may be distinguished from the XR device 2330 and may be operativelyconnected thereto.

The self-driving vehicle 2320 having means for providing an XR/PCC imagemay acquire sensor information from the sensors including a camera, andoutput the generated XR/PCC image based on the acquired sensorinformation. For example, the self-driving vehicle may have an HUD andoutput an XR/PCC image thereto to provide an occupant with an XR/PCCobject corresponding to a real object or an object present on thescreen.

In this case, when the XR/PCC object is output to the HUD, at least apart of the XR/PCC object may be output to overlap the real object towhich the occupant's eyes are directed. On the other hand, when theXR/PCC object is output on a display provided inside the self-drivingvehicle, at least a part of the XR/PCC object may be output to overlapthe object on the screen. For example, the self-driving vehicle mayoutput XR/PCC objects corresponding to objects such as a road, anothervehicle, a traffic light, a traffic sign, a two-wheeled vehicle, apedestrian, and a building.

The virtual reality (VR) technology, the augmented reality (AR)technology, the mixed reality (MR) technology and/or the point cloudcompression (PCC) technology according to the embodiments are applicableto various devices.

In other words, the VR technology is a display technology that providesonly real-world objects, backgrounds, and the like as CG images. On theother hand, the AR technology refers to a technology for showing a CGimage virtually created on a real object image. The MR technology issimilar to the AR technology described above in that virtual objects tobe shown are mixed and combined with the real world. However, the MRtechnology differs from the AR technology makes a clear distinctionbetween a real object and a virtual object created as a CG image anduses virtual objects as complementary objects for real objects, whereasthe MR technology treats virtual objects as objects having the samecharacteristics as real objects. More specifically, an example of MRtechnology applications is a hologram service.

Recently, the VR, AR, and MR technologies are sometimes referred to asextended reality (XR) technology rather than being clearly distinguishedfrom each other. Accordingly, embodiments of the present disclosure areapplicable to all VR, AR, MR, and XR technologies. For suchtechnologies, encoding/decoding based on PCC, V-PCC, and G-PCCtechniques may be applied.

The PCC method/device according to the embodiments may be applied to avehicle that provides a self-driving service.

A vehicle that provides the self-driving service is connected to a PCCdevice for wired/wireless communication.

When the point cloud data transmission and reception device (PCC device)according to the embodiments is connected to a vehicle forwired/wireless communication, the device may receive and process contentdata related to an AR/VR/PCC service that may be provided together withthe self-driving service and transmit the processed content data to thevehicle. In the case where the point cloud data transmission andreception device is mounted on a vehicle, the point cloud transmittingand reception device may receive and process content data related to theAR/VR/PCC service according to a user input signal input through a userinterface device and provide the processed content data to the user. Thevehicle or the user interface device according to the embodiments mayreceive a user input signal. The user input signal according to theembodiments may include a signal indicating the self-driving service.

A transmission device according to embodiments is a device configured totransmit point cloud data, and a reception device according toembodiments is a device configured to receive point cloud data.

The methods/devices according to the embodiments representmethods/devices for transmitting and receiving point cloud dataaccording to the embodiments, a point cloud encoder and a decoderincluded in the transmission device/reception device, a deviceconfigured to generate and parse data to transmit and receive pointcloud data, a processor, and/or methods corresponding thereto.

A point cloud data transmission device according to embodiments mayinclude a point cloud data encoder and a transmitter configured totransmit point cloud data. The point cloud data transmission device mayfurther include a point cloud data encapsulator capable of configuringpoint cloud data in a format for efficient transmission. The encoderconfigured to compress the point cloud data and the encapsulatorconfigured to perform the encapsulation for transmission may becollectively referred to as a point cloud data system. Theabove-described components may be simply referred to as a method/deviceaccording to embodiments in this specification.

The point cloud data reception device according to the embodiments mayinclude a point cloud data decoder and a receiver configured to receivepoint cloud data. The point cloud data reception device may furtherinclude a decapsulator configured to parse the point cloud data from adata structure in a format for efficient reception of the point clouddata. The decoder configured to restore the point cloud data and thedecapsulator configured to perform the decapsulation forreception/parsing may be collectively referred to as a point cloud datasystem. The above-described components may be simply referred to as amethod/device according to embodiments in this specification.

Video-based point cloud compression (V-PCC) described in thisspecification is the same as visual volumetric video-based coding (V3C).The terms V-PCC and V3C according to embodiments may be usedinterchangeably and may have the same meaning.

The method/device according to the embodiments may generate a fileformat for a dynamic point cloud object and provide a signaling methodtherefor (File Encapsulation of Dynamic Point Cloud Object).

FIG. 24 illustrates a V-PCC bitstream according to embodiments.

The V-PCC bitstream 24000 represents a form (i.e., a bitstream form) inwhich point cloud data according to embodiments is transmitted. TheV-PCC bitstream 24000 shown in FIG. 24 may represent the compressedbitstream of FIG. 4 , the bitstream of FIG. 15 , the compressedbitstream received in FIG. 16 , and the bitstream of FIG. 17 , abitstream generated by the multiplexer 18007 in FIG. 18 , and abitstream generated by the demultiplexer in FIG. 19 .

The V-PCC bitstream shown in FIG. 24 may be generated by the XR device1230, the self-driving vehicle 1220, the robot 1210, the AI server 1260,the home appliance 1250, and the smartphone 1240 according to theembodiments shown in FIG. 23 , and may be transmitted to ortransmitted/received between the devices over the cloud network (5G)1200.

The V-PCC bitstream 24000 shown in FIG. 24 may be a bitstream to bereceived by the file/segment encapsulator 20004 of FIG. 20 . That is,the V-PCC bitstream may be a bitstream directly transmitted by the pointcloud data transmission device/method according to the embodiments, ormay represent a bitstream before being encapsulated in the ISOBMFFscheme.

The V-PCC bitstream 24000 shown in FIG. 24 may be video streams and/orimage streams of FIG. 21 , or output from the file/segment insulationunit 21009. It may be a bitstream constituting segments (or files).

The V-PCC bitstream 24000 according to embodiments may include one ormore sample stream V-PCC units 24001. The one or more sample streamV-PCC units 24001 may include a V-PCC unit and a V-PCC unit sizeindicating the size of the V-PCC unit.

The V-PCC bitstream 24000 includes a coded point cloud sequence (CPCS).

The V-PCC unit includes a V-PCC unit header 24001 b and/or a V-PCC unitpayload 24001 c.

The V-PCC unit header 24001 b includes signaling information about datacontained in the V-PCC unit payload according to the embodiments. TheV-PCC unit header according to the embodiments may indicate, forexample, the type of data (e.g., V-PCC parameter set 24002 a, occupancyvideo data 24002 b, geometry video data 24002 c, atlas data 24002 e,and/or attribute video data 24002 d, or the like) contained in the V-PCCunit according to the embodiments. In addition, the V-PCC unit header24001 b according to the embodiments may further include signalinginformation necessary for data contained in the V-PCC unit.

The V-PCC unit payload 24001 c contains point cloud data according toembodiments or information needed to render or reconstruct the pointcloud data.

The V-PCC unit payload 24001 c may include, for example, a V-PCCparameter set 24002 a, occupancy video data 24002 b, geometry video data24002 c, atlas data 24002 e, and/or attribute video data 24002 d. TheV-PCC unit payload 24001 c may carry occupancy video, attribute video,or geometry video. The V-PCC unit payload 24001 c may be composed of oneor more NAL units.

The V-PCC unit payload 24002 according to the embodiments contains pointcloud data according to the embodiments. The point cloud data mayinclude one of occupancy video data, geometry video data, and/orattribute video data of the point cloud data. The point cloud data mayinclude geometry video data encoded using the scheme of pulse codingmodulation (PCM) and/or attribute video data encoded using the PCM.

The V-PCC parameter set 24002 a according to the embodiments representsa parameter set including parameters or signaling information (e.g.,metadata) for the point cloud data according to the embodiments. Forexample, the V-PCC parameter set may include signaling information abouta sequence constituting point cloud data.

The occupancy video data 24002 b is data including occupancy map dataaccording to embodiments. The geometry video data 24002 c includesgeometry video data according to embodiments. The attribute video data24002 d includes attribute video data according to embodiments.

The atlas data 24002 e represents data composed of an attribute (e.g.,texture (patch)) and/or depth of point cloud data.

For example, the syntax of the V-PCC unit according to the embodimentsmay be configured as follows.

Descriptor   vpcc_unit( numBytesInVPCCUnit) {  vpcc_unit_header( ) vpcc_unit_payload( )  while( more_data_in_vpcc_unit )  trailing_zero_8bits /* equal to 0x00*/ f(8) }

FIG. 25 illustrates an example of a V-PCC bitstream according toembodiments.

The V-PCC bitstream according to the embodiments illustrated in FIG. 25represents the V-PCC bitstream 24000 of FIG. 24 .

The V-PCC bitstream shown in FIG. 25 may be generated by the XR device1230, the self-driving vehicle 1220, the robot 1210, the AI server 1260,the home appliance 1250, and the smartphone 1240 according to theembodiments shown in FIG. 23 , and may be transmitted to ortransmitted/received between the devices over the cloud network (5G)1200.

The V-PCC bitstream 25000 according to the embodiments includes one ormore sample stream V-PCC units 25002. The sample stream V-PCC units mayrepresent the sample stream V-PCC units 24001 of FIG. 24 . The samplestream V-PCC unit may be referred to as a V-PCC unit.

The V-PCC bitstream 25000 according to the embodiments may furtherinclude a sample stream V-PCC header 25001 containing information aboutsample stream V-PCC units.

The sample stream V-PCC unit 25002 has several types. Examples of thesample stream V-PCC unit 25002 include a V-PCC unit including a V-PCCparameter set (VPS), and a V-PCC unit including attribute data (AD), aV-PCC unit including occupancy video data (OVD), a V-PCC unit includinggeometry video data (GVD), and/or a V-PCC unit including attribute videodata (AVD).

The V-PCC bitstream 25000 according to the embodiments includes thesample stream V-PCC unit 25002 including a VPS according to theembodiments. The V-PCC bitstream 25000 according to the embodiments mayinclude one or more ore sample stream V-PCC units including one of AD,OVD, GVD, and/or AVD.

25004 shows an example of the syntax of the sample stream V-PCC header25001 according to the embodiments. The sample stream V-PCC header 25004may contain information of ssvh_unit_size_precision_bytes_minus1. Eachsample stream V-PCC unit contains one type of V-PCC unit among VPS, AD,OVD, GVD, and AVD.

ssvh_unit_size_precision_bytes_minus1 plus 1 specifies the precision, inbytes, of the ssvu_vpcc_unit_size element in all sample stream V-PCCunits. ssvh_unit_size_precision_bytes_minus1 may be in the range of 0 to7.

25005 shows an example of the syntax of the sample stream V-PCC unit25002 according to the embodiments. The content of each sample stream VPCC unit is associated with the same access unit as the V-PCC unitcontained in the sample stream V-PCC unit. The V-PCC unit 25002 mayinclude, for example, ssvu_vpcc_unit_size.

ssvu_vpcc_unit_size specifies the size, in bytes, of the subsequentvpcc_unit. The number of bits used to represent ssvu_vpcc_unit_size maybe equal to (ssvh_unit_size_precision_bytes_minus1+1)*8.

vpcc_unit( ), that is, vpcc_unit(ssvu_vpcc_unit_size) represents a V-PCCunit having a size of ssvu_vpcc_unit_size according to embodiments.vpcc_unit(ssvu_vpcc_unit_size) according to the embodiments includes aV-PCC unit header (vpcc_unit_header( )) and/or a V-PCC unit payload(vpcc_unit_payload( )). The V-PCC unit header shown in FIG. 25 mayrepresent the V-PCC unit header 24001 b shown in FIG. 24 .

vpcc_unit( ) according to the embodiments may have, for example, thefollowing syntax.

Descriptor   vpcc_unit( numBytesInVPCCUnit) {  vpcc_unit_header( ) vpcc_unit_payload( )  while( more_data_in_vpcc_unit )  trailing_zero_8bits /* equal to 0x00 */ f(8) }

vpcc_unit_header( ) represents a V-PCC unit header according toembodiments. vpcc_unit payload( ) represents a V-PCC unit payloadaccording to embodiments.

FIG. 26 shows a V-PCC unit and a V-PCC unit header according toembodiments.

FIG. 26 shows the syntax of the above-described V-PCC unit and V-PCCunit header (for example, the V-PCC unit and V-PCC unit header describedabove in FIGS. 24 and 25 ).

A V-PCC bitstream according to embodiments may contain a series of V-PCCsequences.

A V-PCC bitstream contains a series of V-PCC sequences. A vpcc unit typewith a value of vuh_unit_type equal to VPCC_VPS may be expected to bethe first V-PCC unit type in a V-PCC sequence. All other V-PCC unittypes follow this unit type without any additional restrictions in theircoding order. A V-PCC unit payload of a V-PCC unit carrying occupancyvideo, attribute video, or geometry video is composed of one or more NALunits.

A VPCC unit may include a header and a payload.

The VPCC unit header may include the following information based on theVUH unit type.

vuh_unit_type indicates the type of the V-PCC unit 27020 as follows.

vuh_unit_type Identifier V-PCC Unit Type Description 0 VPCC_VPS V-PCCparameter V-PCC level set parameters 1 VPCC_AD Atlas data Atlasinformation 2 VPCC_OVD Occupancy Video Occupancy Data information 3VPCC_GVD Geometry Video Geometry Data information 4 VPCC_AVD AttributeVideo Attribute Data information 5 . . . 31 VPCC_RSVD Reserved —

When vuh_unit_type indicates attribute video data (VPCC_AVD), geometryvideo data (VPCC_GVD), occupancy video data (VPCC_OVD), or atlas data(VPCC_AD), vuh_vpcc_parameter_set ID and vuh_atlas_id is carried in theunit header. A parameter set ID and an atlas ID associated with theV-PCC unit may be delivered.

When the unit type is atlas video data, the header of the unit may carryan attribute index (vuh_attribute_index), an attribute partition index(vuh_attribute_partition_index), a map index (vuh_map_index), and anauxiliary video flag (vuh_auxiliary_video_flag).

When the unit type is geometry video data, vuh_map_index andvuh_auxiliary_video_flag may be carried.

When the unit type is occupancy video data or atlas data, the header ofthe unit may contain additional reserved bits.

vuh_vpcc_parameter_set_id specifies the value ofvps_vpcc_parameter_set_id for the active V-PCC VPS. Through thevpcc_parameter_set_id in the header of the current V-PCC unit, the ID ofthe VPS parameter set may be known and the relationship between theV-PCC unit and the V-PCC parameter set may be announced.

vuh_atlas_id specifies the index of the atlas that corresponds to thecurrent V-PCC unit. Through the vuh_atlas_id in the header of thecurrent V-PCC unit, the index of the atlas may be known, and the atlascorresponding to the V-PCC unit may be announced.

vuh_attribute_index indicates the index of the attribute data carried inthe Attribute Video Data unit.

vuh_attribute_partition_index indicates the index of the attributedimension group carried in the Attribute Video Data unit.

vuh_map_index indicates, when present, the map index of the currentgeometry or attribute stream.

vuh_auxiliary_video_flag equal to 1 indicates that the associatedgeometry or attribute video data unit is a RAW and/or EOM coded pointsvideo only. vuh_auxiliary_video_flag equal to 0 indicates that theassociated geometry or attribute video data unit may contain RAW and/orEOM coded points.

FIG. 27 shows exemplary syntax of a V-PCC parameter set according toembodiments.

The V-PCC parameter set according to the embodiments shown in FIG. 27may represent, for example, the V-PCC parameter set 24002 a of FIG. 24 ,the VPS in the sample stream V-PCC unit 25002 of FIG. 25 , or the V-PCCparameter set included in the V-PCC unit of type VPCC_VPS described withreference to FIG. 26 .

The V-PCC parameter set according to the embodiments shown in FIG. 27may be generated by the point cloud video encoder 10002 of FIG. 1 , theauxiliary patch info compressor 40005 of FIG. 4 , the encoding device100 of FIG. 15 , the patch generator 18000 of FIG. 18 , the videoencoder 20002 and the image encoder 20003 of FIGS. 20 and 21 , or thelike.

The V-PCC parameter set according to the embodiments may be referred toas various terms such as a V3C parameter set and a visual volumetricparameter set. Hereinafter, the term “VPCC” may be replaced with and/orreferred to as “V3C.” For example, vps_vpcc_parameter_set_id informationmay be referred to as vps_v3c_parameter_set_id or the like.

The V-PCC parameter set according to the embodiments may include, forexample, profile_tier_level( ) information, vps_vpcc_parameter_set_id,vps_atlas_count_minus1, and/or vps_extension_present_flag.

profile_tier_level( ) contains V-PCC codec profile related informationand specifies restrictions on the bitstreams and hence limits on thecapabilities needed to decode the bitstreams. Profiles, tiers, andlevels may also be used to indicate interoperability points betweenindividual decoder implementations.

vps_vpcc_parameter_set_id provides an identifier for the V-PCC parameterset (VPS) for reference by other syntax elements.

vps_atlas_count_minus1 plus 1 indicates the total number of supportedatlases in the current bitstream.

vps_extension_present_flag equal to 1 specifies that the syntax elementvps_extension_length is present in vpcc_parameter_set syntax structure.vps_extension_present_flag equal to 0 specifies that syntax elementvps_extension_length is not present.

vps_extension_length_minus1 plus 1 specifies the number ofvps_extension_data_byte elements that follow this syntax element.

vps_extension_data_byte may have any value.

The V-PCC parameter set according to the embodiments may includevps_frame_width, vps_frame_height, vps_map_count_minus1,vps_map_absolute_coding_enabled_flag, vps_auxiliary_video_present_flag,occupancy_information, geometry_information, and/orattribute_information as many as the number of atlases indicated byvps_atlas_count_minus1.

vps_frame_width[j] indicates the V-PCC frame width for the atlas withindex j. For example, vps_frame_width[j] indicates the V-PCC frame widthin terms of integer luma samples for the atlas with index j. This framewidth is the nominal width that is associated with all V-PCC componentsfor the atlas with index j.

vps_frame_height[j] indicates the V-PCC frame height for the atlas withindex j. For example, vps_frame_height[j] indicates the V-PCC frameheight in terms of integer luma samples for the atlas with index j. Thisframe height is the nominal height that is associated with all V-PCCcomponents for the atlas with index j.

vps_map_count_minus1 [j] plus 1 indicates the number of maps used forencoding the geometry and attribute data for the atlas with index j.

vps_multiple_map_streams_present_flag[j] equal to 0 indicates that allgeometry or attribute maps for the atlas with index j are placed in asingle geometry or attribute video stream, respectively.vps_multiple_map_streams_present_flag[j] equal to 1 indicates that allgeometry or attribute maps for the atlas with index j are placed inseparate video streams.

vps_map_absolute_coding_enabled_flag[j][i] equal to 1 indicates that thegeometry map with index i for the atlas with index j is coded withoutany form of map prediction. vps_map_absolute_coding_enabled_flag[j][i]equal to 0 indicates that the geometry map with index i for the atlaswith index j is first predicted from another, earlier coded map, priorto coding.

vps_map_predictor_index_diff[j][i] is used to compute the predictor ofthe geometry map with index i for the atlas with index j whenvps_map_absolute_coding_enabled_flag[j][i] is equal to 0.

vps_auxiliary_video_present_flag[j] equal to 1 indicates that auxiliaryinformation for the atlas with index j, e.g., RAW or EOM patch data, maybe stored in a separate video stream, e.g., the auxiliary video stream.vps_auxiliary_video_present_flag[j] equal to 0 indicates that auxiliaryinformation for the atlas with index j is not stored in a separate videostream.

occupancy_information( ) includes occupancy video related information.

geometry_information( ) includes geometry video related information.

attribute_information( ) includes attribute video related information.

FIG. 28 shows an atlas frame according to embodiments.

A rectangle 28000 shown in FIG. 28 represents one atlas frame. The atlasframe 28000 according to the embodiments may be generated by the patchgenerator 40000 and the patch packer 40001 of FIG. 4 .

The atlas frame 28000 is a 2D rectangular array of atlas samples ontowhich patches are projected. The atlas frame according to theembodiments may mean the atlas frame shown in FIG. 3 .

The atlas frame 28000 may include one or more tiles 28001. That is, theatlas frame may be divided into tiles.

The atlas frame 28000 may be divided into one or more tile rows and oneor more tile columns.

The tile 28001 according to the embodiments is a unit for dividing a 2Dframe. That is, the tile 28001 is a unit for dividing the atlas. Thetile 28001 may represent, for example, a unit for encoding and/ordecoding according to embodiments. A tile may be a rectangular region ofan atlas frame.

A tile group 28802 may contain one or more tiles of the atlas frame28000.

Referring to FIG. 28 , the tile group 28002 contains multiple tiles28001, etc. of the atlas frame 28000. The tile group 28002 constitutes arectangular region of the atlas frame 28000. Referring to FIG. 28 , forexample, the atlas frame 28000 may be partitioned and/or divided into 24tiles (6 tile columns and 4 tile rows). The atlas frame 28000 may bedivided into 9 rectangular tile groups 28002.

FIG. 29 shows an exemplary atlas substream according to embodiments.

The atlas substream represents a sub-bitstream type extracted from aV-PCC bitstream (or V3C bitstream). The atlas substream includes a partof the atlas NAL bitstream.

The V-PCC unit payload 29000 of the V-PCC unit according to theembodiments may contain an atlas sub-bitstream (or atlas substream)shown in FIG. 29 , and the atlas sub-bitstream may contain one or moresample stream NAL units. (A V-PCC unit payload of V-PCC unit carryingthe atlas substream may be composed of one or more sample stream NALunits).

The atlas sub-bitstream according to the embodiments shown in FIG. 29may be composed of one or more network abstraction layer (NAL) units orsample stream NAL units for point cloud data according to theembodiments.

The atlas sub-bitstream according to the embodiments includes a V-PCCsample stream NAL header 29001. A V-PCC unit 29000 according to theembodiments includes one or more sample stream NAL units 29002.

There are various types of NAL units (or sample stream NAL units) 29002according to embodiments. Examples of the NAL unit include a samplestream NAL unit including an atlas sequence parameter set (ASPS), asample stream NAL unit including an adaptation parameter set (AAPS), asample stream NAL unit including an atlas frame parameter set (AFPS), asample stream NAL unit including an atlas tile group (ATP), a samplestream NAL unit including essential SEI, and/or a NAL unit includingnon-essential SEI.

The sample stream NAL header 29001 contains signaling information aboutthe one or more sample stream NAL units 29002. For example, the samplestream NAL header 29001 may containssvh_unit_size_precision_bytes_minus1.

29003 shows an example of the syntax of the sample stream NAL unitheader according to embodiments.

ssvh_unit_size_precision_bytes_minus1 plus 1 may specify, for example,the precision, in bytes, of the ssnu_nal_unit_size element in all samplestream NAL units. ssnh_unit_size_precision_bytes_minus1 may be in therange of 0 to 7.

29004 shows an example of the syntax of the sample stream NAL unitaccording to embodiments.

ssvu_nal_unit_size specifies the size, in bytes, of the subsequentNAL_unit. The number of bits used to represent ssnu_nal_unit_size may beequal to (ssnh_unit_size_precision_bytes_minus1+1)*8.

NAL_unit( ), that is, nal_unit(ssvu_vpcc_unit_size) indicates a NAL unithaving a size of ssvu_nal_unit_size according to the embodiments.

Each sample stream NAL unit includes an atlas sequence parameter set(ASPS), an atlas adaptation parameter set (AAPS), an atlas frameparameter set (AFPS), and atlas tile group information, essential SEI,and/or non-essential SEI.

A supplemental enhancement information (SEI) message containsinformation necessary for operations related to decoding,reconstruction, display, or other purposes. The SEI message according tothe embodiments contains an SEI payload (sei_payload).

The syntax of NAL_unit( ), that is, nal_unit (ssvu_vpcc_unit_size)according to embodiments may be configured as follows.

Descriptor nal_unit( NumBytesInNalUnit) { nal_unit_header( )NumBytesInRbsp = 0 for( i = 2; i < NumBytesInNalUnit; i++ ) rbsp_byte[NumBytesInRbsp++ ] b(8) }

nal_unit_header( ) represents the header of a NAL unit according toembodiments.

NumBytesInNalUnit specifies the size of the NAL unit in bytes.

NumBytesInRbsp is initialized to zero, and indicates the bytes thatbelong to the payload of the NAL unit.

rbsp_byte[i] is the i-th byte of an RBSP.

The syntax of the header of the NAL unit, that is, nal_unit_header( )according to embodiments may be configured as follows.

Descriptor nal_unit_header( ) { nal_forbidden_zero_bit f(1)nal_unit_type u(6) nal_layer_id u(6) nal_temporal_id_plus1 u(3) }

nal_forbidden_zero_bit shall be equal to 0.

nal_unit_type specifies the type of the RBSP data structure contained inthe NAL unit as specified in the table below.

Name of NAL unit nal_unit_type nal_unit_type Content of NAL unit andRBSP syntax structure type class  0 NAL_TRAIL Coded tile group of anon-TSA, non STSA trailing ACL atlas frame atlas_tile_group_layer_rbsp()  1 NAL_TSA Coded tile group of a TSA atlas frame ACLatlas_tile_group_layer_rbsp( )  2 NAL_STSA Coded tile group of an STSAatlas frame ACL atlas_tile_group_layer_rbsp( )  3 NAL_RADL Coded tilegroup of an RADL atlas frame ACL atlas_tile_group_layer_rbsp( )  4NAL_RASL Coded tile group of an RASL atlas frame ACLatlas_tile_group_layer_rbsp( )  5 NAL_SKIP Coded tile group of a skippedatlas frame ACL atlas_tile_group_layer_rbsp( ) 6 . . . 9 NAL_RSV_ACL_6 .. . Reserved non-IRAP ACL NAL unit types ACL NAL_RSV_ACL_9 10NAL_BLA_W_LP Coded tile group of a BLA atlas frame ACL 11 NAL_BLA_W_RADLatlas_tile_group_layer_rbsp( ) 12 NAL_BLA_N_LP 13 NAL_GBLA_W_LP Codedtile group of a GBLA atlas frame ACL 14 NAL_GBLA W RADLatlas_tile_group_layer_rbsp( ) 15 NAL_GBLA_N_LP 16 NAL_IDR_W_RADL Codedtile group of an IDR atlas frame ACL 17 NAL_IDR_N_LPatlas_tile_group_layer_rbsp( ) 18 NAL_GIDR_W_RADL Coded tile group of aGIDR atlas frame ACL 19 NAL_GIDR_N_LP atlas_tile_group_layer_rbsp( ) 20NAL_CRA Coded tile group of a CRA atlas frame ACLatlas_tile_group_layer_rbsp( ) 21 NAL_GCRA Coded tile group of a GCRAatlas frame ACL atlas_tile_group_layer_rbsp( ) 22 NAL_IRAP_ACL_22Reserved IRAP ACL NAL unit types ACL 23 NAL_IRAP_ACL_23 24 . . . 31NAL_RSV_ACL_24 . . . Reserved non-IRAP ACL NAL unit types ACLNAL_RSV_ACL_31 32 NAL_ASPS Atlas sequence parameter set non-ACLatlas_sequence_parameter_set_rbsp( ) 33 NAL_AFPS Atlas frame parameterset non-ACL atlas_frame_parameter_set_rbsp( ) 34 NAL_AUD Access unitdelimiter non-ACL access_unit_delimiter_rbsp( ) 35 NAL_VPCC_AUD V-PCCaccess unit delimiter non-ACL access_unit_delimiter_rbsp( ) 36 NAL_EOSEnd of sequence non-ACL end_of_seq_rbsp( ) 37 NAL_EOB End of bitstreamnon-ACL end_of_atlas_sub_bitstream_rbsp( ) 38 NAL_FD Filler non-ACLfiller_data_rbsp( ) 39 NAL_PREFIX_NSEI Non-essential supplementalenhancement non-ACL 40 NAL_SUFFIX_NSEI information sei_rbsp( ) 41NAL_PREFIX_ESEI Essential supplemental enhancement non-ACL 42NAL_SUFFIX_ESEI information sei_rbsp( ) 43 NAL_AAPS Atlas adaptationparameter set non-ACL atlas_adaptation_parameter_set-rbsp( ) 44 . . . 47NAL_RSV_NACL_44 Reserved non-ACL NAL unit types non-ACL NAL_RSV_NACL_4748 . . . 63 NAL_UNSPEC_48 Unspecified non-ACL NAL unit types non-ACLNAL_UNSPEC_63

nal_layer_id specifies the identifier of the layer to which an ACL NALunit belongs or the identifier of a layer to which a non-ACL NAL unitapplies.

nal_temporal_id_plus1 minus1 specifies a temporal identifier for the NALunit.

Each sample stream NAL unit contains one of atlas parameter sets, i.e.,ASPS, AAPS, AFPS, one or more atlas tile group information, and SEIs.

FIG. 30 shows exemplary syntax of an atlas sequence parameter setaccording to embodiments.

The atlas sequence parameter set according to the embodiments shown inFIG. represents, for example, the ASPS shown in FIG. 29 and described inthe corresponding paragraph.

The atlas sequence parameter set according to the embodiments shown inFIG. may be generated by the point cloud video encoder 10002 of FIG. 1 ,the auxiliary patch info compressor 40005 of FIG. 4 , the encodingdevice 100 of FIG. 15 , the patch generator 18000 of FIG. 18 , the videoencoder 20002 and the image encoder 20003 of FIGS. 20 and 21 , or thelike.

The ASPS according to the embodiments shown in FIG. 30 may includeasps_atlas_sequence_parameter_set_id, asps_frame_width,asps_frame_height, asps_log2_patch_packing_block_size,asps_log2_max_atlas_frame_order_cnt_lsb_minus4,asps_max_dec_atlas_frame_buffering_minus1,asps_long_term_ref_atlas_frames_flag,asps_num_ref_atlas_frame_lists_in_asps,asps_use_eight_orientations_flag, asps_extended_projection_enabled_flag,asps_normal_axis_limits_quantization_enabled_flag,asps_normal_axis_max_delta_value_enabled_flag,asps_remove_duplicate_point_enabled_flag,asps_pixel_deinterleaving_enabled_flag,asps_patch_precedence_order_flag,asps_patch_size_quantizer_present_flag, asps_raw_patch_enabled_flag,asps_eom_patch_enabled_flag,asps_point_local_reconstruction_enabled_flag, 1asps_map_count_minus1,asps_vui_parameters_present_flag, and/or asps_extension_flag.

The ASPS according to the embodiments may contain syntax elements thatapply to zero or more entire coded atlas sequences (CASs) as determinedby the content of a syntax element found in the ASPS referred to by asyntax element found in each tile group header.

asps_atlas_sequence_parameter_set_id provides an identifier for theatlas sequence parameter set for reference by other syntax elements.

asps_frame_width indicates the atlas frame width in terms of integernumber of samples, where a sample corresponds to a luma sample of avideo component.

asps_frame_height indicates the atlas frame height in terms of integernumber of samples, where a sample corresponds to a luma sample of avideo component.

asps_log2_patch_packing_block_size specifies the value of the variablePatchPackingBlockSize. PatchPackingBlockSize is used for the horizontaland vertical placement of the patches within the atlas.

asps_log2_max_atlas_frame_order_cnt_lsb_minus4 specifies the value ofthe variable MaxAtlasFrmOrderCntLsb, which is used in the decodingprocess for the atlas frame order count.

asps_max_dec_atlas_frame_buffering_minus1 plus 1 specifies the maximumrequired size of the decoded atlas frame buffer for the CAS in units ofatlas frame storage buffers.

asps_long_term_ref_atlas_frames_flag equal to 0 specifies that no longterm reference atlas frame is used for inter prediction of any codedatlas frame in the CAS. asps_long_term_ref_atlas_frames_flag equal to 1specifies that long term reference atlas frames may be used for interprediction of one or more coded atlas frames in the CAS.

asps_num_ref_atlas_frame_lists_in_asps specifies the number of theref_list_struct(rlsIdx) syntax structures included in the atlas sequenceparameter set.

asps_use_eight_orientations_flag equal to 0 specifies that the patchorientation index for a patch with index j in a frame with index i,pdu_orientation_index[i][j], is in the range of 0 to 1, inclusive.asps_use_eight_orientations_flag equal to 1 specifies that the patchorientation index for a patch with index j in a frame with index i,pdu_orientation_index[i][j], is in the range of 0 to 7, inclusive.

asps_extended_projection_enabled_flag equal to 0 specifies that thepatch projection information is not signaled for the current atlas tilegroup. asps_extended_projection_enabled_flag equal to 1 specifies thatthe patch projection information is signaled for the current atlas tilegroup.

asps_normal_axis_limits_quantization_enabled_flag equal to 1 specifiesthat quantization parameters shall be signaled and used for quantizingthe normal axis related elements of a patch data unit, a merge patchdata unit, or an inter patch data unit.asps_normal_axis_limits_quantization_enabled_flag equal to 0 specifiesthat no quantization is applied on any normal axis related elements of apatch data unit, a merge patch data unit, or an inter patch data unit.

asps_normal_axis_max_delta_value_enabled_flag equal to 1 specifies thatthe maximum nominal shift value of the normal axis that may be presentin the geometry information of a patch with index i in a frame withindex j will be indicated in the bitstream for each patch data unit, amerge patch data unit, or an inter patch data unit.asps_normal_axis_max_delta_value_enabled_flag equal to 0 specifies thatthe maximum nominal shift value of the normal axis that may be presentin the geometry information of a patch with index i in a frame withindex j shall not be indicated in the bitstream for each patch dataunit, a merge patch data unit, or an inter patch data unit.

asps_remove_duplicate_point_enabled_flag equal to 1 indicates thatduplicated points are not reconstructed for the current atlas, where aduplicated point is a point with the same 2D and 3D geometry coordinatesas another point from a lower index map.asps_remove_duplicate_point_enabled_flag equal to 0 indicates that allpoints are reconstructed.

asps_pixel_deinterleaving_enabled_flag equal to 1 indicates that thedecoded geometry and attribute videos for the current atlas containspatially interleaved pixels from two maps.asps_pixel_deinterleaving_flag equal to 0 indicates that the decodedgeometry and attribute videos corresponding to the current atlas containpixels from only a single map.

For example, when the value of asps_pixel_deinterleaving_enabled_flag is1, the ASPS according to the embodiments may includeasps_pixel_deinterleaving_map_flag as many as asps_map_count_minus1 plus1.

asps_map_count_minus1 plus 1 indicates the number of maps that may beused for encoding the geometry and attribute data for the current atlas)

asps_pixel_deinterleaving_map_flag equal to 1 indicates that decodedgeometry and attribute videos corresponding to a map with index i in thecurrent atlas contain spatially interleaved pixels corresponding to twomaps. asps_pixel_deinterleaving_map_flag[i] equal to 0 indicates thatdecoded geometry and attribute videos corresponding to the map index iin the current atlas contain pixels corresponding to a single map.

asps_patch_precedence_order_flag equal to 1 indicates that patchprecedence for the current atlas is the same as the decoding order.asps_patch_precedence_order_flag equal to 0 indicates that patchprecedence for the current atlas is the reverse of the decoding order.

asps_patch_size_quantizer_present_flag equal to 1 indicates that thepatch size quantization parameters are present in an atlas tile groupheader. asps_patch_size_quantizer_present_flag equal to 0 indicates thatthe patch size quantization parameters are not present.

asps_eom_patch_enabled_flag equal to 1 indicates that the decodedoccupancy map video for the current atlas contains information relatedto whether intermediate depth positions between two depth maps areoccupied. asps_eom_patch_enabled_flag equal to 0 indicates that thedecoded occupancy map video does not contain information related towhether intermediate depth positions between two depth maps areoccupied.

When the value of asps_eom_patch_enabled_flag is 1, the ASPS accordingto the embodiments may further includeasps_auxiliary_video_enabled_flag.

asps_point_local_reconstruction_enabled_flag equal to 1 indicates thatpoint local reconstruction mode information may be present in thebitstream for the current atlas.asps_point_local_reconstruction_enabled_flag equal to 0 indicates thatno information related to the point local reconstruction mode is presentin the bitstream for the current atlas.

When the value of asps_eompatch_enabled_flag is 0, the ASPS according tothe embodiments may further include asps_eom_fix_bit_count_minus1.

asps_eom_fix_bit_count_minus1 plus 1 indicates the size in bits of theEOM codeword.

When the value of asps_point_local_reconstruction_enabled_flag is 1, theASPS according to the embodiments may further includeasps_point_local_reconstruction_information.

asps_point_local_reconstruction_information includes the point localreconstruction mode information to support the missed pointreconstruction at the decoder side.

When the value of asps_pixel_deinterleaving_enabled_flag orasps_point_local_reconstruction_enabled_flag is 1, the ASPS according tothe embodiments may include asps_surface_thickness_minus1.

asps_surface_thickness_minus1 plus 1 specifies the maximum absolutedifference between an explicitly coded depth value and interpolateddepth value when asps_pixel_deinterleaving_enabled_flag orasps_point_local_reconstruction_enabled_flag is equal to 1.

asps_vui_parameters_present_flag equal to 1 specifies that thevui_parameters( ) syntax structure is present.asps_vui_parameters_present_flag equal to 0 specifies that thevui_parameters( ) syntax structure is not present.

asps_extension_flag equal to 0 specifies that noasps_extension_data_flag syntax elements are present in the ASPS RBSPsyntax structure.

asps_extension_data_flag may have any value.

rbsp_trailing_bits is used for the purpose of filling the remaining bitswith 0 for byte alignment after adding 1, which is a stop bit, toindicate the end of RBSP data.

FIG. 31 shows exemplary syntax of an atlas frame parameter set accordingto embodiments.

The atlas frame parameter set according to the embodiments shown in FIG.31 represents, for example, the AFPS shown in FIG. 29 and described inthe corresponding paragraph.

The atlas frame parameter set according to the embodiments shown in FIG.31 may be generated by the point cloud video encoder 10002 of FIG. 1 ,the auxiliary patch info compressor 40005 of FIG. 4 , the encodingdevice 100 of FIG. 15 , the patch generator 18000 of FIG. 18 , the videoencoder 20002 and the image encoder 20003 of FIGS. 20 and 21 , or thelike.

The atlas frame parameter set (AFPS) according to the embodimentscontains a syntax structure containing syntax elements that apply tozero or more entire coded atlas frames.

The AFPS according to the embodiments may further containafps_atlas_frame_parameter_set_id, afps_atlas_sequence_parameter_set_id,atlas_frame_tile_information( ), afps_output_flag_present_flag,afps_num_ref_idx_default_active_minus1, afps_additional_lt_afoc_lsb_len,afps_3d_pos_x_bit_count_minus1, afps_3d_pos_y_bit_count_minus1,afps_lod_mode_enabled_flag, afps_override_eom_for_depth_flag,afps_raw_3d_pos_bit_count_explicit_mode_flag,afps_fixed_camera_model_flag, and/or afps_extension_flag.

afps_atlas_frame_parameter_set_id identifies the atlas frame parameterset for reference by other syntax elements.

afps_atlas_sequence_parameter_set_id specifies the value ofasps_atlas_sequence_parameter_set_id for the active atlas sequenceparameter set.

afps_output_flag_present_flag equal to 1 indicates that theatgh_frame_output_flag syntax element is present in the associated tilegroup headers. afps_output_flag_present_flag equal to 0 indicates thatthe atgh_frame_output_flag syntax element is not present in theassociated tile group headers.

afps_num_ref_idx_default_active_minus1 plus 1 specifies the inferredvalue of the variable NumRefIdxActive for the tile group withatgh_num_ref_idx_active_override_flag equal to 0.

afps_additional_lt_afoc_lsb_len specifies the value of the variableMaxLtAtlasFrmOrderCntLsb that is used in the decoding process for thereference atlas frame.

afps_3d_pos_x_bit_count_minus1 plus 1 specifies the number of bits inthe fixed-length representation of pdu_3d_pos_x[j] of patch with index jin an atlas tile group that refers to afps_atlas_frame_parameter_set_id.

afps_3d_pos_y_bit_count_minus1 plus 1 specifies the number of bits inthe fixed-length representation of pdu_3d_pos_y[j] of patch with index jin an atlas tile group that refers to afps_atlas_frame_parameter_set_id.

afps_lod_mode_enabled_flag equal to 1 indicates that the LOD parametersmay be present in a patch. afps_lod_mode_enabled_flag equal to 0indicates that the LOD parameters are not be present in a patch.

afps_override_eom_for_depth_flag equal to 1 indicates that the values ofafps_eom_number_of_patch_bit_count_minus1 andafps_eom_max_bit_count_minus1 are explicitly present in the bitstream.afps_override_eom_for_depth_flag equal to 0 indicates that the values ofafps_eom_number_of_patch_bit_count_minus1 andafps_eom_max_bit_count_minus1 are implicitly derived.

afps_raw_3d_pos_bit_count_explicit_mode_flag equal to 1 indicates thatthe number of bits in the fixed-length representation of rpdu_3d_pos_x,rpdu_3d_pos_y, and rpdu_3d_pos_z is explicitly coded byatgh_raw_3d_pos_axis_bit_count_minus1 in the atlas tile group header.

afps_extension_flag equal to 0 specifies that noafps_extension_data_flag syntax elements are present in the AFPS RBSPsyntax structure.

afps_extension_data_flag may have any value.

When the value of afps_override_eom_for_depth_flag is 1, the AFPSaccording to the embodiments may further containafps_eom_number_of_patch_bit_count_minus1 and/orafps_eom_max_bit_count_minus1.

afps_eom_number_of_patch_bit_count_minus1 plus 1 specifies the number ofbits used to represent the number of geometry patches associated with anEOM attribute patch in an atlas frame that is associated with this atlasframe parameter set.

afps_eom_max_bit_count_minus1 plus 1 specifies the number of bits usedto represent the number of EOM points per geometry patch associated withan EOM attribute patch in an atlas frame that is associated with thisatlas frame parameter set.

FIG. 32 shows exemplary syntax of atlas frame tile information accordingto embodiments.

Atlas frame tile information (AFTI) according to the embodimentsrepresents atlas_frame_tile_information( ) shown/described withreference to FIG. 31 .

The AFTI according to the embodiments may includeafti_single_tile_in_atlas_frame_flag.

afti_single_tile_in_atlas_frame_flag equal to 1 specifies that there isonly one tile in each atlas frame referring to the AFPS.afti_single_tile_in_atlas_frame_flag equal to 0 specifies that there ismore than one tile in each atlas frame referring to the AFPS.

When the value of afti_single_tile_in_atlas_frame_flag is 0 (or whenthere are two or more tiles in each atlas frame referring to the AFPS,the AFTI according to the embodiments may includeafti_uniform_tile_spacing_flag, afti_single_tile_per_tile_group_flag,and/or afti_signalled_tile_group_flag.

afti_uniform_tile_spacing_flag equal to 1 specifies that tile column androw boundaries are distributed uniformly across the atlas frame and maybe signaled using the syntax elements, afti_tile_cols_width_minus1 andafti_tile_rows_height_minus1, respectively.afti_uniform_tile_spacing_flag equal to 0 specifies that tile column androw boundaries may or may not be distributed uniformly across the atlasframe and may be signaled using the syntax elementsafti_num_tile_columns_minus1 and afti_num_tile_rows_minus1 and a list ofsyntax element pairs afti_tile_column_width_minus1[i] andafti_tile_row_height_minus1[i].

When the value of afti_uniform_tile_spacing_flag is 1, the AFTIaccording to the embodiments may further includeafti_tile_cols_width_minus1 and/or afti_tile_cols_width_minus1.

afti_tile_cols_width_minus1 plus 1 specifies the width of the tilecolumns excluding the rightmost tile column of the atlas frame in unitsof 64 samples.

afti_tile_rows_height_minus1 plus 1 specifies the height of the tilerows excluding the bottom tile row of the atlas frame in units of 64samples.

When the value of afti_uniform_tile_spacing_flag is 0, the AFTIaccording to the embodiments may include afti_num_tile_columns_minus1,afti_num_tile_rows_minus1, afti_tile_column_width_minus1, and/orafti_tile_row_height_minus1.

afti_num_tile_columns_minus1 plus 1 specifies the number of tile columnspartitioning the atlas frame.

afti_num_tile_rows_minus1 specifies the number of tile rows partitioningthe atlas frame.

afti_tile_column_width_minus[i] plus 1 specifies the width of the i-thtile column in units of 64 samples.

afti_tile_row_height_minus1[i] plus 1 specifies the height of the i-thtile row in units of 64 samples.

afti_single_tile_per_tile_group_flag equal to 1 specifies that each tilegroup that refers to this AFPS includes one tile.afti_single_tile_per_tile_group_flag equal to 0 specifies that a tilegroup that refers to this AFPS may include more than one tile.

When the value of afti_single_tile_per_tile_group_flag is 0, that is,when each tile group referring to the AFPS contains more than one tile,the AFTI includes afti_num_tile_groups_in_atlas_frame_minus1,afti_bottom_right_tile_idx_delta, and afti_signalled_tile_group_id_flag.

afti_num_tile_groups_in_atlas_frame_minus1 plus 1 specifies the numberof tile groups in each atlas frame referring to the AFPS.

afti_top_left_tile_idx[i] specifies the tile index of the tile locatedat the top-left corner of the i-th tile group.

afti_bottom_right_tile_idx_delta[i] specifies the difference between thetile index of the tile located at the bottom-right corner of the i-thtile group and afti_top_left_tile_idx[i].

afti_signalled_tile_group_id_flag equal to 1 specifies that the tilegroup ID for each tile group is signaled.

When the value of afti_signalled_tile_group_id_flag is 1, that is, whenthe tile group ID for each tile group is signaled, the AFTI according tothe embodiments may further includeafti_signalled_tile_group_id_length_minus1 and/or afti_tile_group_id.

afti_signalled_tile_group_id_length_minus1 plus 1 specifies the numberof bits used to represent the syntax element afti_tile_group_id[i] whenpresent, and the syntax element atgh_address in tile group headers.

afti_tile_group_id[i] specifies the tile group ID of the i-th tilegroup. The length of the afti_tile_group_id[i] syntax element isafti_signalled_tile_group_id_length_minus1+1 bits.

FIG. 33 shows exemplary syntax of an atlas adaptation parameter set andatlas camera parameters according to embodiments.

The atlas adaptation parameter set according to the embodiments shown inFIG. 31 represents, for example, the AAPS shown in FIG. 29 and describedin the corresponding paragraph.

The atlas camera parameters according to the embodiments shown in FIG.33 may be contained in the atlas adaptation parameter set according tothe embodiments.

The atlas adaptation parameter set shown in FIG. 33 may be generated bythe point cloud video encoder 10002 of FIG. 1 , the auxiliary patch infocompressor 40005 of FIG. 4 , the encoding device 100 of FIG. 15 , thepatch generator 18000 of FIG. 18 , the video encoder 20002 and the imageencoder 20003 of FIGS. 20 and 21 , or the like.

An atlas adaptation parameter set (AAPS) RBSP according to embodimentsincludes parameters that can be referred to by the coded tile group NALunits of one or more coded atlas frames. At most one AAPS RBSP isconsidered active at any given moment during the operation of thedecoding process, and the activation of any particular AAPS RBSP resultsin the deactivation of the previously-active AAPS RBSP.

The AAPS according to the embodiments may containaaps_atlas_adaptation_parameter_set_id,aaps_camera_parameters_present_flag, and/or aaps_extension_flag.

aaps_atlas_adaptation_parameterset_id identifies the atlas adaptationparameter set for reference by other syntax elements.

aaps_camera_parameters_present_flag equal to 1 specifies that cameraparameters are present in the current AAPS.aaps_camera_parameters_present_flag equal to 0 specifies that cameraparameters for the current AAPS are not be present.

When the value of aaps_camera_parameters_present_flag is 1, the AAPS mayfurther contain atlas_camera_parameters( ) according to embodiments.

atlas_camera_parameters( ) according to the embodiments may containacp_camera_model.

acp_camera_model indicates the camera model for point cloud frames thatare associated with the current adaptation parameter set as listed inthe table below.

acp_camera_model Name of acp_camera_model 0 UNSPECIFIED 1 Orthographiccamera model 2-255 RESERVED

When the value of acp_camera_model is 1, that is, when the camera modelfor the point cloud frames associated with the adaptation parameter setis the orthographic camera model, the ACP according to the embodimentsmay include acp_scale_enabled_flag, acp_offset_enabled_flag, and/oracp_rotation_enabled_flag.

acp_scale_enabled_flag equal to 1 indicates that scale parameters forthe current camera model are present. acp_scale_enabled_flag equal to 0indicates that scale parameters for the current camera model are notpresent.

When the value of acp_scale_enabled_flag is 1, the ACP according to theembodiments may further contain a scale parameter for the current cameramodel, for example, acp_scale_on_axis.

acp_scale_on_axis[d] specifies the value of the scale, Scale[d], alongthe d axis for the current camera model. The value of d may be in therange of 0 to 2, inclusive, with the values of 0, 1, and 2 correspondingto the X, Y, and Z axis, respectively.

acp_offset_enabled_flag equal to 1 indicates that offset parameters forthe current camera model are present. acp_offset_enabled_flag equal to 0indicates that offset parameters for the current camera model are notpresent.

When the value of acp_offset_enabled_flag is 1, the ACP according to theembodiments may further include a scale parameter for the current cameramodel, for example, acp_offset_on_axis[d].

acp_offset_on_axis[d] indicates the value of the offset, Offset[d],along the d axis for the current camera model where d is in the range of0 to 2, inclusive. The values of d equal to 0, 1, and 2 correspond tothe X, Y, and Z axis, respectively.

acp_rotation_enabled_flag equal to 1 indicates that rotation parametersfor the current camera model are present. acp_rotation_enabled_flagequal to 0 indicates that rotation parameters for the current cameramodel are not present.

When the value of acp_rotation_enabled_flag is 1, the ACP may includeacp_rotation_qx, acp_rotation_qy, and acp_rotation_qz.

acp_rotation_qx specifies the x component, qX, for the rotation of thecurrent camera model using the quaternion representation.

acp_rotation_qy specifies the y component, qY, for the rotation of thecurrent camera model using the quaternion representation.

acp_rotation_qz specifies the z component, qZ, for the rotation of thecurrent camera model using the quaternion representation.

aaps_extension_flag equal to 0 specifies that noaaps_extension_data_flag syntax elements are present in the AAPS RBSPsyntax structure.

aaps_extension_data_flag may have any value.

FIG. 34 shows atlas tile group layer information according toembodiments.

The atlas tile group layer information according to the embodimentsshown in FIG. 34 represents, for example, the atlas tile group layershown in FIG. 29 and described in the corresponding paragraph.

The atlas tile group layer according to the embodiments shown in FIG. 34may be generated by the point cloud video encoder 10002 of FIG. 1 , theauxiliary patch info compressor 40005 of FIG. 4 , the encoding device100 of FIG. 15 , the patch generator 18000 of FIG. 18 , the videoencoder 20002 and the image encoder 20003 of FIGS. 20 and 21 , or thelike.

The atlas tile group layer according to the embodiments may containatlas_tile_group_header( ).

atlas_tile_group_header( ) according to the embodiments may containatgh_atlas_frame_parameter_set_id,atgh_atlas_adaptation_parameter_set_id, atgh_address, atgh_type,atgh_atlas_frm_order_cnt_lsb, and atgh_additional_afoc_lsb_present_flag.

atgh_atlas_frame_parameter_set_id specifies the value ofafps_atlas_frame_parameter_set_id for the active atlas frame parameterset for the current atlas tile group.

atgh_atlas_adaptation_parameter_set_id specifies the value ofaaps_atlas_adaptation_parameter_set_id for the active atlas adaptationparameter set for the current atlas tile group.

atgh_address specifies the tile group address of the tile group. Whennot present, the value of atgh_address is inferred to be equal to 0. Thetile group address is the tile group ID of the tile group. The length ofatgh_address is afti_signalled_tile_group_id_length_minus1+1 bits. Ifafti_signalled_tile_group_id_flag is equal to 0, the value ofatgh_address is in the range of 0 toafti_num_tile_groups_in_atlas_frame_minus1, inclusive. Otherwise, thevalue of atgh_address is in the range of 0 to2^((afti_signalled_tile_group_id_length_minus1+1))−1, inclusive.

atgh_type specifies the coding type of the current atlas tile groupaccording to the table below.

atgh_type Name of atgh_type 0 P_TILE_GRP (Inter atlas tile group) 1I_TILE_GRP (Intra atlas tile group) 2 SKIP_TILE_GRP (SKIP atlas tilegroup) 3-. . . RESERVED

atgh_atlas_output_flag affects the decoded atlas output and removalprocesses.

atgh_atlas_frm_order_cnt_lsb specifies the atlas frame order countmodulo MaxAtlasFrmOrderCntLsb for the current atlas tile group.

atgh_ref_atlas_frame_list_sps_flag equal to 1 specifies that thereference atlas frame list of the current atlas tile group is derivedbased on one of the ref_list_struct(rlsIdx) syntax structures in theactive ASPS. atgh_ref_atlas_frame_list_sps_flag equal to 0 specifiesthat the reference atlas frame list of the current atlas tile list isderived based on the ref_list_struct(rlsIdx) syntax structure that isdirectly included in the tile group header of the current atlas tilegroup.

atgh_ref_atlas_frame_list_idx specifies the index, into the list of theref_list_struct(rlsIdx) syntax structures included in the active ASPS,of the ref_list_struct(rlsIdx) syntax structure that is used forderivation of the reference atlas frame list for the current atlas tilegroup.

atgh_additional_afoc_lsb_present_flag[j] equal to 1 specifies thatatgh_additional_afoc_lsb_val[j] is present for the current atlas tilegroup. atgh_additional_afoc_lsb_present_flag[j] equal to 0 specifiesthat atgh_additional_afoc_lsb_val[j] is not present.

atgh_additional_afoc_lsb_val [j] specifies the value ofFullAtlasFrmOrderCntLsbLt[RlsIdx][j] for the current atlas tile group.

atghpos_min_z_quantizer specifies the quantizer that is to be applied tothe pdu_3d_pos_min_z[p] value of the patch p. If atghpos_min_z_quantizeris not present, the value thereof is inferred to be equal to 0.

atgh_pos_delta_max_z_quantizer specifies the quantizer that is to beapplied to the pdu_3d_pos_delta_max_z[p] value of the patch with indexp. If atgh_pos_delta_max_z_quantizer is not present, the value thereofis inferred to be equal to 0.

atgh_patch_size_x_info_quantizer specifies the value of the quantizerPatchSizeXQuantizer that is to be applied to the variablespdu_2d_size_x_minus1 [p], mpdu_2d_delta_size_x[p],ipdu_2d_delta_size_x[p], rpdu_2d_size_x_minus1 [p], andepdu_2d_size_x_minus1[p] of a patch with index p. Ifatgh_patch_size_x_info_quantizer is not present, the value thereof maybe inferred to be equal to asps_log2patch_packing_block_size.

atgh_patch_size_y_info_quantizer specifies the value of the quantizerPatchSizeYQuantizer that is to be applied to the variablespdu_2d_size_y_minus1 [p], mpdu_2d_delta_size_y[p],ipdu_2d_delta_size_y[p], rpdu_2d_size_y_minus1 [p], andepdu_2d_size_y_minus1[p] of a patch with index p. Ifatgh_patch_size_y_info_quantizer is not present, the value thereof maybe inferred to be equal to asps_log2_patch_packing_block_size.

atgh_raw_3d_pos_axis_bit_count_minus1 plus 1 specifies the number ofbits in the fixed-length representation of rpdu_3d_pos_x, rpdu_3d_pos_y,and rpdu_3d_pos_z.

atgh_num_ref_idx_active_override_flag equal to 1 specifies that thesyntax element atgh_num_ref_idx_active_minus1 is present for the currentatlas tile group. atgh_num_ref_idx_active_override_flag equal to 0specifies that the syntax element atgh_num_ref_idx_active_minus1 is notpresent. If atgh_num_ref_idx_active_override_flag is not present, thevalue thereof may be inferred to be equal to 0.

atgh_num_ref_idx_active_minus1 specifies the maximum reference index forreference the atlas frame list that may be used to decode the currentatlas tile group. When the value of NumRefIdxActive is equal to 0, noreference index for the reference atlas frame list may be used to decodethe current atlas tile group.

FIG. 35 shows reference list structure information according toembodiments.

The reference list structure (ref_list struct( )) according to theembodiments may represent, for example, ref_list_struct( ) shown in FIG.34 .

ref_list_struct( ) according to the embodiments may have an identifier(rlsIdx) for identifying a reference list structure as a parameter.

ref_list_struct( ) according to the embodiments may includenum_ref_entries.

num_ref_entries specifies the number of entries in theref_list_struct(rlsIdx) syntax structure.

ref_list_struct( ) according to the embodiments may further includest_ref_atlas_frame_flag, abs_delta_afoc_st, and/or afoc_lsb_lt as manyas the value of num_ref_entries, namely, the number of entries.

st_ref_atlas_frame_flag[rlsIdx][i] equal to 1 specifies that the i-thentry in the ref_list_struct(rlsIdx) syntax structure is a short termreference atlas frame entry. st_ref_atlas_frame_flag[rlsIdx][i] equal to0 specifies that the i-th entry in the ref_list_struct(rlsIdx) syntaxstructure is a long term reference atlas frame entry. When not present,the value of st_ref_atlas_frame_flag[rlsIdx][i] may be inferred to beequal to 1.

When the i-th entry is the first short term reference atlas frame entryin ref_list_struct(rlsIdx) syntax structure,abs_delta_afoc_st[rlsIdx][i] specifies the absolute difference betweenthe atlas frame order count values of the current atlas tile group andthe atlas frame referred to by the i-th entry. When the i-th entry is ashort term reference atlas frame entry but not the first short termreference atlas frame entry in the ref_list_struct(rlsIdx) syntaxstructure, abs_delta_afoc_st[rlsIdx][ i] specifies the absolutedifference between the atlas frame order count values of the atlasframes referred to by the i-th entry and by the previous short termreference atlas frame entry in the ref_list_struct(rlsIdx) syntaxstructure.

strpf_entry_sign_flag[rlsIdx][ i] equal to 1 specifies that i-th entryin the syntax structure ref_list_struct(rlsIdx) has a value greater thanor equal to 0. strpf_entry_sign_flag[rlsIdx][ i] equal to 0 specifiesthat the i-th entry in the syntax structure ref_list_struct(rlsIdx) hasa value less than 0. When not present, the value ofstrpf_entry_sign_flag[rlsIdx][i] may be inferred to be equal to 1.

afoc_lsb_lt[rlsIdx][i] specifies the value of the atlas frame ordercount modulo MaxAtlasFrmOrderCntLsb of the atlas frame referred to bythe i-th entry in the ref_list_struct(rlsIdx) syntax structure. Thelength of the afoc_lsb_lt[rlsIdx][i] syntax element isasps_log2_max_atlas_frame_order_cnt_lsb_minus4+4 bits.

FIG. 36 shows an atlas tile group data unit according to embodiments.

The atlas tile group data unit according to the embodiments representsthe atlas tile group data unit (atlas_tile_group_data_unit) included inthe atlas tile group layer information shown in FIG. 34 .

The atlas tile group data unit according to the embodiments includesatgdu_patch_mode[p].

atgdu_patch_mode[p] indicates the patch mode for the patch with index pin the current atlas tile group. A tile group withatgh_type=SKIP_TILE_GRP implies that the entire tile group informationis copied directly from the tile group with the same atgh_address asthat of the current tile group that corresponds to the first referenceatlas frame.

Patch mode types for atlas tile groups of type I_TILE_GRP may bespecified as follows.

atgdu_patch_mode Identifier Description 0 I_INTRA Non-predicted Patchmode 1 I_RAW RAW Point Patch mode 2 I_EOM EOM Point Patch mode 3-13I_RESERVED Reserved modes 14  I_END Patch termination mode

Patch mode types for atlas tile groups of type P_TILE_GRP may bespecified as follows.

atgdu_patch_mode Identifier Description 0 P_SKIP Patch Skip mode 1P_MERGE Patch Merge mode 2 P_INTER Inter predicted Patch mode 3 P_INTRANon-predicted Patch mode 4 P_RAW RAW Point Patch mode 5 P_EOM EOM PointPatch mode 6-13 P_RESERVED Reserved modes 14  P_END Patch terminationmode

Patch mode types for atlas tile groups of type SKIP_TILE_GRP may bespecified as follows.

atgdu_patch_mode Identifier Description 0 P_SKIP Patch Skip mode

The atlas tile group data unit according to the embodiments may furtherinclude patch information data (patch_information_data( )) according toembodiments.

For example, the patch information data (patch_information_data( )) mayhave a syntax structure as follows.

Descriptor patch_information_data (patchIdx, patchMode ) { if( atgh_type== SKIP_TILE_GR ) skip_patch_data_unit( patchIdx ) else if( atgh_type ==P_TILE_GR ) { if( patchMode == P_SKIP ) skip_patch_data_unit( patchIdx )else if( patchMode == P_MERGE ) merge_patch_data_unit( patchIdx ) elseif( patchMode == P_INTRA ) patch_data_unit( patchIdx ) else if(patchMode == P_INTER ) inter_patch_data_unit( patchIdx ) else if(patchMode == P_RAW ) raw_patch_data_unit( patchIdx ) else if( patchMode== P_EOM ) eom_patch_data_unit( patchIdx ) } else if( atgh_type ==I_TILE_GR ) { if( patchMode == I_INTRA ) patch_data_unit( patchIdx )else if( patchMode == I_RAW ) raw_patch_data_unit( patchIdx ) else if(patchMode == I_EOM ) eom_patch_data_unit( patchIdx ) } }

The patch information data (patch_information_data( )) according to theembodiments may include a patch data unit. An example of the patch dataunit is shown in FIG. 37 .

FIG. 37 shows exemplary syntax of a patch data unit according toembodiments.

pdu_2d_pos_x[p] specifies the x-coordinate (or left offset) of thetop-left corner of the patch bounding box for patch p in the currentatlas tile group, tileGroupIdx, expressed as a multiple ofPatchPackingBlockSize.

pdu_2d_pos_y[p] specifies the y-coordinate (or top offset) of thetop-left corner of the patch bounding box for patch p in the currentatlas tile group, tileGroupIdx, expressed as a multiple ofPatchPackingBlockSize.

pdu_2d_size_x_minus1 [p] plus 1 specifies the quantized width value ofthe patch with index p in the current atlas tile group, tileGroupIdx.

pdu_2d_size_y_minus1 [p] plus 1 specifies the quantized height value ofthe patch with index p in the current atlas tile group, tileGroupIdx.

pdu_3d_pos_x[p] specifies the shift to be applied to the reconstructedpatch points in patch with index p of the current atlas tile group alongthe tangent axis.

pdu_3d_pos_y[p] specifies the shift to be applied to the reconstructedpatch points in patch with index p of the current atlas tile group alongthe bitangent axis.

pdu_3d_pos_min_z[p] specifies the shift to be applied to thereconstructed patch points in patch with index p of the current atlastile group along the normal axis.

pdu_3d_pos_delta_max_z[p], if present, specifies the nominal maximumvalue of the shift expected to be present in the reconstructed bitdepthpatch geometry samples, after conversion to their nominalrepresentation, in patch with index p of the current atlas tile groupalong the normal axis.

pdu_projection_id[p] specifies the values of the projection mode and ofthe index of the normal to the projection plane for the patch with indexp of the current atlas tile group.

pdu_orientation_index[p] indicates the patch orientation index for thepatch with index p of the current atlas tile group as the below.

The orientation index according to the embodiments may be specified asfollows.

x Identifier Rotation(x) Offset(x) 0 FPO_NULL $\begin{bmatrix}1 & 0 \\0 & 1\end{bmatrix}$ $\begin{bmatrix}0 \\0\end{bmatrix}$ 1 FPO_SWAP $\begin{bmatrix}0 & 1 \\1 & 0\end{bmatrix}$ $\begin{bmatrix}0 \\0\end{bmatrix}$ 2 FPO_ROT90 $\begin{bmatrix}0 & {- 1} \\1 & 0\end{bmatrix}$ $\begin{bmatrix}{{{Patch}2{{dSizeY}\lbrack p\rbrack}} - 1} \\0\end{bmatrix}$ 3 FPO_ROT180 $\begin{bmatrix}{- 1} & 0 \\0 & {- 1}\end{bmatrix}$ $\begin{bmatrix}{{{Patch}2{{dSizeX}\lbrack p\rbrack}} - 1} \\{{{Patch}2{{dSizeY}\lbrack p\rbrack}} - 1}\end{bmatrix}$ 4 FPO_ROT270 $\begin{bmatrix}0 & 1 \\{- 1} & 0\end{bmatrix}$ $\begin{bmatrix}0 \\{{{Patch}2{{dSizeX}\lbrack p\rbrack}} - 1}\end{bmatrix}$ 5 FPO_MIRROR $\begin{bmatrix}{- 1} & 0 \\0 & 1\end{bmatrix}$ $\begin{bmatrix}{{{Patch}2{{dSizeX}\lbrack p\rbrack}} - 1} \\0\end{bmatrix}$ 6 FPO_MROT90 $\begin{bmatrix}0 & {- 1} \\{- 1} & 0\end{bmatrix}$ $\begin{bmatrix}{{{Patch}2{{dSizeY}\lbrack p\rbrack}} - 1} \\{{{Patch}2{{dSizeX}\lbrack p\rbrack}} - 1}\end{bmatrix}$ 7 FPO_MROT180 $\begin{bmatrix}1 & 0 \\0 & {- 1}\end{bmatrix}$ $\begin{bmatrix}0 \\{{{Patch}2{{dSizeY}\lbrack p\rbrack}} - 1}\end{bmatrix}$

pdu_lod_enabled_flag[p] equal to 1 specifies that the LOD parameters arepresent for the current patch p. pdu_lod_enabled_flag[p] equal to 0specifies that no LOD parameters are present for the current patch.

pdu_lod_scale_x_minus1[p] specifies the LOD scaling factor to be appliedto the local x coordinate of a point in a patch with index p of thecurrent atlas tile group, prior to its addition to the patch coordinatePatch3dPosX[p].

pdu_lod_scale_y[p] specifies the LOD scaling factor to be applied to thelocal y coordinate of a point in a patch with index p of the currentatlas tile group, prior to its addition to the patch coordinatePatch3dPosY[p].

The point cloud data transmission device according to the embodimentstransmits a V-PCC bitstream of the structure shown in FIGS. 24 to 37 ,thereby enabling the transmitter to effectively perform multiplexing.Due to this structure, the point cloud data may provide an efficientaccess to the bitstream in units of V-PCC units for the receptiondevice. In addition, with this configuration, the transmission devicemay provide an effect of effectively storing and transmitting the atlasstream of the V-PCC bitstream in a track in a file.

SEI messages/information for data processing and rendering in the V-PCCbit stream may be effectively stored and transmitted in a file.

FIG. 38 shows a structure of a file carrying point cloud data accordingto embodiments.

The file according to the embodiments shown in FIG. 38 may be, forexample, a file according to the ISOBMFF format. The file according tothe embodiments may be generated by, for example, the file/segmentencapsulation module 10003 of FIG. 1 or the file/segment encapsulator20004, 21009 of FIGS. 20 and 21 . The file according to the embodimentsmay include a V3C bitstream according to the embodiments shown in FIGS.24 and/or 25 . The file according to the embodiments may include some orall of the parameters shown in FIGS. 26 to 37 . The file according tothe embodiments contains point cloud data according to embodiments.

Point cloud data according to the embodiments may be in a format of anISOBMFF file. The ISOBMFF file may be composed of objects called boxes.That is, all data may be contained in one or more boxes.

A box may include a box header, which may include a size and a type ofthe box. The point cloud data according to the embodiments may includean ftyp box 38000 whose box type is ‘ftyp’, a meta box 38001 whose boxtype is ‘meta’, a moov box 38002 whose box type is ‘moov’, and an mdatbox 38003 whose box type is ‘mdat’.

The ftyp box 38000 may contain information indicating the type of theISOBMFF file according to embodiments.

The meta box 38001 may contain metadata information about the pointcloud data according to embodiments.

The moov box 38002 may contain information about one or more tracks inwhich the point cloud data according to the embodiments is transmitted.

The moov box 38002 according to the embodiments may include a box 38002a containing information about a track for transmitting attributeinformation of the point cloud data, a box 38002 b containinginformation about a track for transmitting occupancy information of thepoint cloud data, a box 38002 c containing information about a track fortransmitting geometry information of the point cloud data, and/or a box38002 d containing information about a track for transmitting V-PCCinformation of the point cloud data.

The mdat box 38003 may include a point cloud bitstream containing thepoint cloud data according to embodiments. The point cloud bitstreamaccording to the embodiments may include a video coded attributebitstream 38003 a, a video coded occupancy bitstream 38003 b, a videocoded geometry bitstream 38003 c, and/or a patch sequence data bitstream38003 d.

The video coded attribute bitstream 38003 a, the video coded occupancybitstream 38003 b, the video coded geometry bitstream 38003 c, and/orthe patch sequence data bitstream 38003 d according to the embodimentsmay be carried by one or more video frames.

The video coded attribute bitstream 38003 a refers to attributeinformation of the point cloud data, encoded by the V-PCC encoderaccording to the embodiments.

The video coded occupancy bitstream 38003 b refers to occupancyinformation of the point cloud data, encoded by the V-PCC encoderaccording to the embodiments.

The video coded geometry bitstream 38003 c refers to geometryinformation of the point cloud data, encoded by the V-PCC encoderaccording to the embodiments.

The patch sequence data bitstream 38003 d refers to patch sequence dataof the point cloud data according to the embodiments.

The 2D video tracks are encoded according to a video encoder accordingto embodiments.

In the sample entry, an extra box may be inserted which may document therole of the video stream contained in this track, in the V-PCC system.

A track reference may be inserted from the V-PCC patch data track to thevideo track, to establish the membership of the video track in thespecific point cloud based on the patch track.

The track-header flags may be set to 0 to indicate that the track doesnot contribute directly to the overall layup of the movie, butcontributes to the V-PCC system.

Tracks belonging to the same V-PCC sequence are time-aligned. Samplesthat contribute to the same point cloud frame across the differentvideo-encoded component tracks and the V-PCC track may have the samepresentation time.

A V-PCC track may contain sequence parameter sets and samples carryingthe payloads of non-video encoded information V-PCC units. Here, thenon-video encoded information V-PCC units may mean units whose V-PCCunit types are, for example, VPCC_SPS and VPCC_PDG.

This track may also provide track references to other tracks containingsamples carrying the payloads of a video compressed V-PCC unit. Here,the other tracks may represent units whose V-PCC unit types are, forexample, VPCC_GVD, VPCC_AVD, and VPCC_OVD.

The samples containing video-coded elementary streams for geometry data,which are payloads of V-PCC units of type VPCC_GVD, may be included inone or more video streams.

The samples containing video-coded elementary streams for attributedata, which are payloads of V-PCC units of type VPCC_AVD, may beincluded in one or more video streams.

The samples containing a video-coded elementary stream for occupancy mapdata, which are payloads of V-PCC units of type VPCC_OVD, may beincluded in one or more video streams.

Synchronization between the elementary streams in the component tracksmay be handled by the ISO BMFF track timing structures (ctts and cslg,or equivalent mechanisms in movie fragments).

Samples that contribute to the same point cloud frame across differentvideo encoded component tracks and the V-PCC track may have the samecomposition time. The V-PCC parameter sets used for such samples have adecoding time equal or prior to the composition time of the frame.

FIG. 39 shows a structure of a file carrying point cloud data accordingto embodiments.

The file according to the embodiments shown in FIG. 39 may be, forexample, a file according to the ISOBMFF format. The file according tothe embodiments may be generated by, for example, the file/segmentencapsulation module 10003 of FIG. 1 or the file/segment encapsulator20004, 21009 of FIGS. 20 and 21 . The file according to the embodimentsmay include a V3C bitstream according to the embodiments shown in FIGS.24 and/or 25 . The file according to the embodiments may include some orall of the parameters shown in FIGS. 26 to 37 . The file according tothe embodiments contains point cloud data according to embodiments.

FIG. 39(A) illustrates point cloud data carried by one track in a fileaccording to embodiments.

Referring to FIG. 39(A), in the embodiments, the point cloud data (pointcloud video #1) may be carried by one V-PCC bitstream track. The V-PCCbitstream track may be referred to as a V3C bitstream track, a V-PCCtrack, a V3C track, or the like. As shown in FIG. 39(A), encapsulatingpoint cloud data in a single track to be transmitted may be referred toas single-track encapsulation.

Referring to FIG. 39(A), the V3C bitstream according to the embodimentsshown in FIGS. 24 and/or 25 may be contained in samples for a single V3Ctrack or in a metadata box or the like for the V3C track.

FIG. 39(B) illustrates point cloud data carried by multiple tracks in afile according to embodiments.

Referring to FIG. 39(B), a single file includes multiple tracks. Themultiple tracks may include, for example, a track related to parameters,patches, atlases, and the like of the point cloud data (e.g., a V-PCCtrack), an occupancy map related track (e.g., an occupancy video track),a geometry video related track (e.g., a geometry video track), and/or anattribute video related track (an attribute video track). That is, oneor more point cloud videos or images may be stored in a single file.Encapsulating a file of this structure may be referred to as multi-trackencapsulation. For example, the structure of the file shown in FIG. 38may be a multi-track encapsulated file.

Referring to FIG. 39(C), a file according to the embodiments may containpoint cloud videos according to embodiments. The file according to theembodiments may contain a point cloud video and/or one or more pointcloud images according to embodiments. The point cloud video (or image)may represent one or more objects constituting point cloud data, or maybe a frame constituting point cloud data in a specific time period.

The point cloud data reception device according to embodiments may playback point cloud data in the file. The point cloud data reception devicemay play back some or all of the point cloud data at the same time. Thefile according to the embodiments is required to provide groupinginformation about point cloud videos or images that need to be played atthe same time. Accordingly, metadata for the point cloud data accordingto the embodiments may include grouping information for playback and/orcontrol information for playback. The grouping information for playbackand/or the control information for playback may not change within thefile and may change over time.

There may be various methods of encapsulating and transmitting (V-PCC)point cloud data according to embodiments, that is, V-PCC systems (V3Csystems). Hereinafter, an exemplary method of encapsulating andtransmitting (V-PCC) point cloud data, that is, an exemplary V-PCCsystem (V3C system) will be described.

Video-based point cloud compression (V-PCC) represents the volumetricencoding of point cloud visual information. A V-PCC bitstream (includingan encoded point cloud sequence (CPCS)) contains V-PCC units (V3C units)according to embodiments, including V3C parameter set data, a codedatlas bitstream, a 2D video coded occupancy map bitstream, a 2D videoencoded geometry bitstream, zero or more 2D encoded attributebitstreams.

First, a volumetric visual media header according to embodiments will bedescribed.

The volumetric visual track may be, for example, a V-PCC track. Thevolumetric visual track may be identified by a volumetric visual mediahandler type ‘vols’ in a Handler Box in a media box and a volumetricvisual media header. Multiple volumetric visual tracks may be present ina file.

-   -   Box Type: ‘vvhd’    -   Container: Medi aInformati onB ox    -   Mandatory: Yes    -   Quantity: Exactly one

Volumetric tracks may use the VolumetricVisualMediaHeaderBox in theMediaInformationBox.

  aligned(8) class VolumetricVisualMediaHeaderBox extendsFullBox(‘vvhd’, version = 0, 1) { }

“version” is an integer that specifies the version of this box.

A V-PCC track sample entry according to embodiments will be described.The V-PCC track sample entry may be contained in the track box in theV-PCC track in the file.

-   -   Sample Entry Type: ‘vpc1’, ‘vpcg’    -   Container: SampleDescriptionBox (‘stsd’)    -   Mandatory: A ‘vpc1’ or ‘vpcg’ sample entry is mandatory.    -   Quantity: One or more sample entries may be present.

V-PCC tracks may use VolumetricVisualSampleEntry having a sample entrytype ‘vpc1’ or ‘vpcg’. The V-PCC volumetric sample entry according tothe embodiments may include VPCCConfigurationBox defined as follows. TheVPCCConfigurationBox may include VPCCDecoderConfigurationRecord (V-PCCconfiguration record box). All data present at the same time in thearray of setup vpcc units may be stored in sample_stream_vpcc_unitstogether with ssvu_vpcc_unit_size by configuring a header providedherein.

Volumetric visual tracks shall use the volumetric visual sample entry.The volumetric visual sample entry may be configured as follows.

  class VolumetricVisualSampleEntry(codingname) extends SampleEntry(codingname){  unsigned int(8)[32] compressor_name; }

compressor_name is a name, for informative purposes. This parameter isformatted in a fixed 32-byte field, with the first byte set to thenumber of bytes to be displayed, followed by that number of bytes ofdisplayable data encoded using UTF-8, and then padding to complete 32bytes in total.

Hereinafter, a common data structure contained in a V-PCC track (presentin the sample entry) or a video-coded V-PCC component track (present inscheme information) according to embodiments will be described.

An example of the V-PCC unit header box will be described.

Headers of V-PCC units (V3C units) according to the embodiments may beencapsulated into a V-PCC unit header box according to embodiments.

The V-PCC unit header box may be present in both the V-PCC track (in thesample entry) and/or all video-coded V-PCC component tracks (e.g., ageometry video track, an attribute video track, an occupancy videotrack, etc.) (in the scheme information). The V-PCC unit header boxincludes a V-PCC unit header (“vpcc_unit_header( ) unit_header;”) fordata carried by the respective tracks.

  aligned(8) class VPCCUnitHeaderBox extends FullBox (‘vunt’, version =0, 0) {  vpcc_unit_header( )  unit_header; }

An example of the V-PCC decoder configuration box will be described.

The V-PCC decoder configuration box containsVPCCDecoderConfigurationRecord. The V-PCC decoder configuration boxaccording to the embodiments may have the following syntax.

   class VPCCConfigurationBox extends Box(‘vpcC’) { VPCCDecoderConfigurationRecord( ) VPCCConfig; }

This record may contain a version field. This specification definesversion 1 of this record.

  aligned(8) class VPCCDecoderConfigurationRecord {  unsigned int(8)configurationVersion = 1;  unsigned int(2) lengthSizeMinusOne;  bit(1)reserved = 1;  unsigned int(5) numOfVPCCParameterSets;  for (i=0; i <numOfVPCCParameterSets; i++) {  unsigned int(16) VPCCParameterSetLength; vpcc_unit(VPCCParameterSetLength) vpccParameterSet; // as defined inISO/IEC 23090-5 }  unsigned int(8) numOfSetupUnitArrays;  for (j=0; j <numOfSetupUnitArrays; j++) {   bit(1) array_completeness;   bit(1)reserved = 0;   unsigned int(6) NAL_unit_type;   unsigned int(8)numNALUnits;   for (i=0; i < numNALUnits; i++) {    unsigned int(16)SetupUnitLength;    nal_unit(SetupUnitLength) setupUnit; // as definedin ISO/IEC 23090-5   } } }

configurationVersion is a version field.

lengthSizeMinusOne plus 1 indicates the length of the NALUnitLengthfield in a V-PCC sample in the stream to which this configuration recordapplies. For example, a size of one byte is indicated with a value of 0.The value of this field may be equal tossnh_unit_size_precision_bytes_minus1 in sample_stream_nal_header( ) forthe atlas substream.

numOfVPCCParameterSets specifies the number of V-PCC parameter set unitssignaled in the decoder configuration record.

VPCCParameterSetLength indicates the size of the vpccParameterSet field.

vpccParameterSet indicates a V-PCC unit of type VPCC_VPS carryingvpcc_parameter_set( ) according to the embodiments. TheVPCCParameterSet; array according to the embodiments may includevpccParameterSet described above.

numOfSetupUnitArrays indicates the number of arrays of atlas NAL unitsof the indicated type(s).

array_completeness equal to 1 indicates that all atlas NAL units of thegiven type are in the following array and none are in the stream.array_completeness equal to 0 indicates that additional atlas NAL unitsof the indicated type may be in the stream. The default and permittedvalues may be constrained by the sample entry name.

NAL_unit_type indicates the type of the atlas NAL units in the followingarray. It may be restricted to take one of the values indicating aNAL_ASPS, NAL_AFPS, NAL_AAPS, NAL_PREFIX_ESEI, NAL_SUFFIX_ESEI,NAL_PREFIX_NSEI, or NAL_SUFFIX_NSEI atlas NAL unit.

numNALUnits indicates the number of atlas NAL units of the indicatedtype included in the configuration record for the stream to which thisconfiguration record applies. The SEI array may only contain SEImessages.

SetupUnitLength indicates the size, in bytes, of the setupUnit field.This field includes the size of both the NAL unit header and the NALunit payload, but does not include the length field itself.

setupUnit may contain a NAL unit of type NAL_ASPS, NAL_AFPS, NAL AAPS,NAL_PREFIX_ESEI, NAL_PREFIX_NSEI, NAL_SUFFIX_ESEI, or NAL_SUFFIX_NSEI.When this field is present, NAL PREFIX ESEI, NAL_PREFIX_NSEI,NAL_SUFFIX_ESEI, or NAL_SUFFIX_NSEI may contain SEI messages thatprovide information on the entire stream. The SEI message may be, forexample, user-data SEI.

The setupUnit array may include atlas parameter sets that are constantfor the stream referred to by the sample entry in which the decoderconfiguration record is present. The atlas parameter set according tothe embodiments may represent NAL units (or a NAL unit) withNAL_unit_type having NAL_ASPS, NAL_AFPS, and/or NAL_AAPS.

The V-PCC atlas parameter set may be encapsulated in a sample groupdescription entry and stored in a file.

Track grouping means grouping tracks associated with each other.

An entity may represent, for example, a track (timed track, etc.) and/ornon-timed items. Non-timed V-PCC data may be referred to as non-timedvolumetric data, non-timed V3C data, or the like.

Multi-Track Container for V-PCC Bitstream

Hereinafter, a process of encapsulating a V-PCC bitstream into amulti-track container according to embodiments will be described.

V-PCC units in a V-PCC bitstream according to the embodiments may bemapped to individual tracks based on the V-PCC container. The V-PCCcontainer may represent a multi-track ISOBMFF V-PCC container. Tracks ina multi-track ISOBMFF V-PCC container may be divided into two types:V-PCC track and V-PCC component track.

V-PCC component tracks are restricted video scheme tracks which carry 2Dvideo encoded data for the occupancy map, geometry, and attributesub-bitstreams of the V-PCC bitstream. The following conditions may besatisfied for V-PCC component tracks:

-   -   a) in the sample entry, a new box is inserted which documents        the role of the video stream contained in this track, in the        V-PCC system;    -   b) a track reference may be introduced from the V-PCC track, to        the V-PCC component track. The membership of the V-PCC component        track in the specific point cloud represented by the V-PCC track        may be established by the track reference;    -   c) the track-header flags may be set to 0 to indicate that this        track does not contribute directly to the overall layup of the        movie but contributes to the V-PCC system.

Tracks belonging to the same V-PCC sequence may be time-aligned. Samplesthat contribute to the same point cloud frame across the differentvideo-encoded V-PCC component tracks and the V-PCC track may have thesame presentation time. The V-PCC atlas sequence parameter sets andatlas frame parameter sets used for such samples may have a decodingtime equal or prior to the composition time of the point cloud frame.All tracks belonging to the same V-PCC sequence may have the sameimplicit or explicit edit lists.

Synchronization between the elementary streams in the component tracksmay be handled by the ISOBMFF track timing structures (stts, ctts, andcslg), or equivalent mechanisms in movie fragments.

The sync samples in the V-PCC track and V-PCC component tracks may ormay not be time-aligned.

In the absence of time-alignment, random access may involve pre-rollingthe various tracks from different sync start-times, to enable startingat the desired time. In the case of time-alignment (e.g. required by aV-PCC profile such as the basic toolset profile as defined in V-PCC),the sync samples of the V-PCC track should be considered as the randomaccess points for the V-PCC content, and random access may be performedby only referencing the sync sample information of the V-PCC track.

Based on this layout, a V-PCC ISOBMFF container may include thefollowing:

-   -   1) A V-PCC track which contains V-PCC parameter sets and atlas        sub-bitstream parameter sets (in the sample entry) and samples        carrying atlas sub-bitstream NAL units. This track may include        track references to other tracks carrying the payloads of video        compressed V-PCC units (i.e., units of types VPCC_OVD, VPCC_GVD,        and VPCC_AVD);    -   2) A restricted video scheme track where the samples contain        access units of a video-coded elementary stream for occupancy        map data (e.g., payloads of V-PCC units of type VPCC_OVD);    -   3) One or more restricted video scheme tracks where the samples        contain access units of video-coded elementary streams for        geometry data (i.e., payloads of V-PCC units of type VPCC_GVD);        and    -   4) Zero or more restricted video scheme tracks where the samples        contain access units of video-coded elementary streams for        attribute data (e.g., payloads of V-PCC units of type VPCC_AVD).

The V-PCC track sample entry will be described.

V-PCC tracks according to the embodiments use VPCCSampleEntry.

VPCCSampleEntry may extend VolumetricVisualSampleEntry with a sampleentry type of ‘vpc1’ or ‘vpcg’. A VPCC track sample entry may contain aV-PCC Configuration Box (VPCCConfigurationBox).

The V-PCC track sample entry may have the following properties.

-   -   Sample Entry Type: ‘vpc1’, ‘vpcg’    -   Container: SampleDescriptionBox    -   Mandatory: A ‘vpc1’ or ‘vpcg’ sample entry is mandatory.    -   Quantity: One or more sample entries may be present

Under the ‘vpc1’ sample entry, all atlas sequence parameter sets, atlasframe parameter sets, or V-PCC SEIs (or SEI messages) may be present inthe setupUnit array. Under the ‘vpcg’ sample entry, the atlas sequenceparameter sets, atlas frame parameter sets, or V-PCC SEIs may be presentin this array, or in the stream. BitRateBox may be present in the V-PCCvolumetric sample entry to signal the bit rate information of the V-PCCtrack.

The VPCCSampleEntry according to the embodiments may include configinformation indicating VPCCConfigurationBox, and unit header informationindicating VPCCUnitHeaderBox.

Single-Track Container for V-PCC Bitstream

Single-track encapsulation of V-PCC data means encapsulating the V-PCCbitstream and/or V-PCC data in a single track according to embodiments.Here, the encapsulated track may be referred to as a V-PCC bitstreamtrack. Single-track encapsulation of V-PCC data requires the V-PCCencoded elementary bitstream to be represented by a single-trackdeclaration.

Single-track encapsulation of PCC data may be utilized for simpleISOBMFF encapsulation of a V-PCC encoded bitstream. Such a bitstream maybe directly stored in a single track without further processing. V-PCCunit header data structures may be stored in the bitstream as it is. Asingle track container for V-PCC data may be provided to media workflowsfor further processing (e.g., multi-track file generation, transcoding,DASH segmentation, etc.).

The V-PCC bitstream track will be described.

V-PCC bitstream tracks use VolumetricVisualSampleEntry with a sampleentry type of ‘vpe1’ or ‘vpeg’. A VPCC bitstream sample entry contains aVPCCConfigurationBox.

Under the ‘vpe1’ sample entry, all atlas sequence parameter sets, atlasframe parameter sets, and SEIs may be in the setupUnit array. Under the‘vpeg’ sample entry, atlas sequence parameter sets, atlas frameparameter sets, and SEIs may be present in this array, or in the stream.

Samples (i.e., V-PCC bitstream samples) carried based on the V-PCCbitstream track will be described. A V-PCC bitstream sample containszero or more V-PCC units (e.g., V-PCC access unit) which belong to thesame presentation time. A sample may be a sync sample or decoding-wisedependent on other samples of the V-PCC bitstream track.

A V-PCC bitstream sync sample will be described. A V-PCC bitstream syncsample may satisfy all the following conditions: 1) It is independentlydecodable; 2) None of the samples that come after the sync sample (indecoding order) have any decoding dependency on any sample prior to thesync sample; and 3) All samples that come after the sync sample (indecoding order) are successfully decodable.

A V-PCC bitstream sub-sample will be described. A V-PCC bitstreamsub-sample may be a V-PCC unit which is contained in a V-PCC bitstreamsample. A V-PCC bitstream track may contain one SubSampleInformationBoxin SampleTableBox, or in TrackFragmentBox of each of MovieFragmentBoxes.

The 32-bit unit header of the V-PCC unit which represents the sub-samplemay be copied to the 32-bit codec_specific_parameters field of thesub-sample entry in the SubSampleInformationBox. The V-PCC unit type ofeach sub-sample is identified by parsing the codec_specific_parametersfield of the sub-sample entry in the SubSampleInformationBox. As thepoint cloud data transmission device according to the embodimentsencapsulates the point cloud data using this method, the receptiondevice may efficiently access the point cloud bitstream. Furthermore,this configuration may allow the reception device to efficiently processthe data of a point cloud bitstream and effectively access informationnecessary for rendering, thereby reducing delays occurring duringdecoding and rendering of point cloud data.

FIG. 40 shows an exemplary operation of encapsulating point cloud dataand metadata related to the point cloud data according to embodiments.

FIG. 40 shows an exemplary encapsulated file for non-timed V-PCC data(e.g., image data) according to embodiments.

FIG. 40 may show the structure of a file encapsulated when thefile/segment encapsulator 20004, 21009 and/or the file/segmentdecapsulator 22000 according to the embodiments of FIGS. 20 to 22delivers image data. Even when the image data is delivered, the pointcloud data according to the embodiments may be encapsulated as a singleitem or multiple items.

On the other hand, the example of the encapsulated file shown in FIG. 28may show the structure of a file encapsulated when the file/segmentencapsulation encapsulator 20004, 21009 and/or the file/segmentdecapsulator 22000 according to the embodiments of FIGS. 20 to 22delivers video data (e.g., a single track or multiple tracks).

FIG. 40 shows an encapsulation structure of non-timed V-PCC data.Non-timed V-PCC data represents point cloud data that does not move overtime. Non-timed V-PCC data may be referred to as non-timed volumetricdata, non-timed V3C data, or the like.

The non-timed V-PCC data may be stored in a file as image items. A newhandler type 4CC code ‘vpcc’ may be defined and stored in the HandlerBoxof the MetaBox in order to indicate the presence of V-PCC items, V-PCCunit items and other V-PCC encoded content representation information.

A V-PCC item including non-timed V-PCC data according to embodimentswill be described.

A V-PCC item is an item which represents an independently decodableV-PCC access unit. A new item type 4CC code ‘vpci’ may be defined toidentify V-PCC items. V-PCC items may be stored in V-PCC unit payload(s)in the atlas sub-bitstream. If PrimaryItemBox is present, item_id inthis box shall be set to indicate a V-PCC item. The V-PCC item may bereferred to as a V3C item or a visual volumetric video-based coded item.

A V-PCC unit item is an item which represents a V-PCC unit data. V-PCCunit items store V-PCC unit payload(s) of occupancy, geometry, andattribute video data units. A V-PCC unit item shall store only one V-PCCaccess unit related data. The V-PCC unit item may be referred to as aV3C unit item or a visual volumetric video-based coded unit item.

An item type 4CC code for a V-PCC unit item may be set depending on thecodec used to encode corresponding video data units. A V-PCC unit itemshall be associated with corresponding V-PCC unit header item propertyand codec specific configuration item property.

V-PCC unit items are marked as hidden items because it is not meaningfulto display independently.

In order to indicate the relationship between a V-PCC item and V-PCCunits, three new item reference types with 4CC codes, ‘pcco’, ‘pccg’ and‘pcca’ are defined. Item reference is defined “from” a V-PCC item “to”the related V-PCC unit items. The 4CC codes of item reference types are:

-   -   1) ‘pcco’ (or v3vo): the referenced V-PCC unit item(s) contain        the occupancy video data units;    -   2) ‘pccg’ (or v3vg): the referenced V-PCC unit item(s) contain        the geometry video data units; and    -   3) ‘pcca’ (or v3va): the referenced V-PCC unit item(s) contain        the attribute video data units.

V-PCC related item properties will be described. Descriptive itemproperties are defined to carry the V-PCC parameter set information andV-PCC unit header information, respectively. The V-PCC-related itemproperties may include, for example, a V-PCC configuration itemproperty, a V-PCC unit header item property, a V-PCC view formation itemproperty, a V-PCC rendering parameter item property, and a V-PCC objectrendering information item property.

The V-PCC related item properties may be referred to as V3C related itemproperties, and the V-PCC unit header information may be referred to asV3C unit header information.

The V-PCC configuration item property will be described.

-   -   Box Type: ‘vpcp’    -   Property type: Descriptive item property    -   Container: ItemPropertyContainerBox    -   Mandatory (per item): Yes (for a V-PCC item of type ‘vpci’)    -   Quantity (per item): One or more (for a V-PCC item of type        ‘vpci’)

V-PCC parameter sets are stored as descriptive item properties and areassociated with the V-PCC items.

The V-PCC configuration item property may be referred to as a V3Cconfiguration item property.

The VPCC configuration property (VPCCConfigurationProperty) according tothe embodiments may have the following syntax.

  aligned(8) class vpcc_unit_payload_struct ( ) {  unsigned int(16)vpcc_unit_payload_size;  vpcc_unit_payload( ); } aligned(8) classVPCCConfigurationProperty extends ItemProperty(‘vpcc’) { vpcc_unit_payload_struct( )[ ]; }

vpcc_unit_payload_size specifies the size of the vpcc_unit_paylod( ).

The V-PCC unit header item property will be described.

-   -   Box Types: ‘vent’    -   Property type: Descriptive item property    -   Container: ItemPropertyContainerBox    -   Mandatory (per item): Yes, for a V-PCC item of type ‘vpci’ and        for a V-PCC unit item    -   Quantity (per item): One

  aligned(8) class VPCCUnitHeaderProperty ( ) extendsItemFullProperty(‘vunt’, version=Ø, Ø) {  vpcc_unit_header( ); }

V-PCC unit header is stored as descriptive item properties and isassociated with the V-PCC items and the V-PCC unit items.

The V-PCC unit header item property may be referred to as a V3C unitheader item property.

As the point cloud data transmission device according to the embodimentsencapsulates the point cloud data using this method, the receptiondevice may efficiently access the point cloud bitstream. Furthermore,this configuration may allow the reception device to efficiently processthe data of a point cloud bitstream and effectively access informationnecessary for rendering, thereby reducing delays occurring duringdecoding and rendering of point cloud data.

FIG. 41 shows an exemplary SEI message structure according toembodiments.

FIG. 41 may show syntax of an SEI message (e.g., the SupplementalEnhancement Information (SEI) message described above in FIGS. 20 to 22,29, 37, and 39 ) according to embodiments. Various methods for storingthe SEI message described in this figure in a V-PCC track according tothe embodiments (e.g., the track for transmitting V-PCC information inFIG. 2 , the V-PCC track in FIG. 38 ) may be presented. For example, theV-PCC track may store the SEI message in a V-PCC configuration recordbox (e.g., VPCCDecoderConfigurationRecord in FIG. 39 ), a sample entry(e.g., the sample entry in FIGS. 38 and 39 ), and/or a sample (e.g., thesample of FIGS. 28 to 30, 32, and 37 to 39 ). The position where the SEImessage according to the embodiments is stored in the V-PCC track is notlimited to the above-described example. The V-PCC track according to theembodiments may be referred to as a track for atlas data, a track foratlas, a V-PCC atlas track, and/or a V3C atlas track.

The SEI message according to the embodiments may be referred to as SEIinformation. The SEI message according to the embodiments may be usedfor decoding, reconstruction, display, or other purposes. The SEImessage according to the embodiments may represent an essential SEImessage or a non-essential SEI message. The non-essential SEI messageaccording to the embodiments may not be used in the above-describeddecoding process. The essential SEI message according to the embodimentsmay be essentially included in the VPCC bitstream (e.g., the VPCCbitstream described with reference to FIGS. 24 and 25 ), and may not beremoved from the VPCC bitstream. Essential SEI messages according to theembodiments may be classified into the following two types:

-   -   1) Type-A essential SEI message: The Type-A essential SEI        message may contain information required to check bitstream        conformance and for output timing decoder conformance. Every        V-PCC decoder conforming to point A should not discard any        relevant Type-A essential SEI messages and may need to consider        the same for bitstream conformance and for output timing decoder        conformance; and    -   2) Type-B essential SEI message: V-PCC decoders that intend to        conform to a particular reconstruction profile should not        discard any relevant Type-B essential SEI messages and may need        to be used for 3D point cloud reconstruction and conformance        purposes.

As described above with reference to FIG. 29 , sei_rbsp( ) 41000 mayinclude an SEI message according to embodiments.

The SEI message according to the embodiments may contain sei_payload.Part 41001 shows the structure of sei_payload according to theembodiments.

The point cloud data transmission device according to the embodimentsmay encapsulate the SEI message described in this figure as variouspositions and transmit the same to the reception device. That is, thetransmission device may change the storage position (or encapsulationposition) of the SEI message such that the reception device mayefficiently access the point cloud data bitstream. This configurationmay enable the reception device to efficiently process the point cloudbitstream and effectively access the information necessary forrendering, thereby reducing latency that may occur during decoding andrendering of the point cloud data.

FIG. 42 shows VPCC SEI message structure information and atlas aparameter set structure according to embodiments

FIG. 42 shows an example of VPCC SEI message (or SEI information)structure information 42000 and VPCC atlas parameter set structureinformation 42001 according to embodiments. The VPCC SEI messagestructure information described with reference to FIG. 42 may representinformation on the SEI message described above with reference to FIG. 41and may contain an SEI message. The VPCC atlas parameter set structureinformation described with reference to FIG. 42 may representinformation on the atlas parameter set described above with reference toFIG. 39 and may contain an atlas parameter set.

The VPCC SEI message structure information and VPCC atlas parameter setstructure information described shown in FIG. 42 may be encapsulated inthe form of a box. For example, the VPCC SEI message structureinformation may be encapsulated in a VPCC SEI info box (VPCCSEIInfoBOX),and the VPCC atlas parameter set structure information may beencapsulated in a VPCC atlas parameter set box (VPCCAPSBox).

A file containing point cloud data according to embodiments may storeone or more point cloud videos or images. A file may carry the pointcloud data based on multiple tracks or image items. For example, a filemay have a file structure as shown in FIGS. 39 and 40 .

VPCCSEIInfoBOX according to the embodiments may contain VPCC SEI messagestructure information (VPCCSEIInfoStrct( )). The VPCCSEIInfoStrct( )according to the embodiments may represent information about an SEImessage (e.g., the SEI message described with reference to FIG. 41 )contained in the file. The VPCCSEIInfoBOX according to the embodimentsmay be present at various positons within the file (e.g., the filedescribed with reference to FIGS. 39 to 40 ). For example, theVPCCSEIInfoBOX may be contained in the metadata box for the VPCC (orV3C) bitstream described with reference to FIGS. 24 and 25 . TheVPCCSEIInfoBOX according to the embodiments may have the followingsyntax.

  aligned(8) class VPCCSEIInfoBox extends Box(‘vsei’) { VPCCSEIInfoStruct( );  }

As described above, the VPCCSEIInfoBOX according to the embodimentscontains VPCCSEIInfoStruct( ). VPCCSEIInfoStruct( ) according to theembodiments represents the above-described VPCC SEI message structureinformation. VPCCSEIInfoStruct( ) according to the embodiments maycontain numEssentialSEIs, ESEI_type, ESEI_length, ESEI_byte,numNonEssentialSEIs, NSEI_type, NSEI_length, and/or NSEI_byte.

numEssentialSEIs may indicate the number of essential SEI messages(e.g., essential SEI messages described with reference to FIG. 41 )signaled by the VPCC SEI message structure information according to theembodiments.

VPCCSEIInfoStruct( ) according to the embodiments may further containESEI_type, ESEI_length, and ESEI_byte based on the index i. The index iaccording to the embodiments may be greater than or equal to 0, and maybe less than the value indicated by the above-describednumEssentialSEIs.

ESEI_type may indicate the type of the essential SEI message signaled bythe VPCC SEI message structure information according to the embodiments.

ESEI_length may indicate the byte length of an essential SEI messagesignaled by VPCCSEIInfoStruct( ) according to the embodiments.

ESEI_byte may contain an essential SEI message signaled byVPCCSEIInfoStruct( ) according to the embodiments, and contain anessential SEI atlas NAL unit that has nal_unit_type (e.g., the NAL unittype described with reference to FIG. 39 ) equal to NAL PREFIX ESEIand/or NAL SUFFIX ESEI. The nal_unit_type is the same as or similar tothat described with reference to FIG. 39 .

numNonEssentialSEIs may indicate the number of non-essential SEImessages (e.g., the non-essential SEI messages described with referenceto FIG. 41 ) signaled by VPCCSEIInfoStruct( ) according to theembodiments.

VPCCSEIInfoStruct( ) according to the embodiments may further containNSEI_type, NSEI_length, and/or NSEI_byte based on the index i. The indexi according to the embodiments may be greater than or equal to 0, andmay be less than the value indicated by the above-describednumNonEssentialSEIs.

NSEI_type may indicate the type of a non-essential SEI message signaledby VPCCSEIInfoStruct( ) according to the embodiments.

NSEI_length may indicate the byte length of the non-essential SEImessage signaled by VPCCSEIInfoStruct( ) according to the embodiments.

NSEI_byte may contain a non-essential SEI message signaled byVPCCSEIInfoStruct( ) according to the embodiments, and contain anessential SEI atlas NAL that has nal_unit_type (e.g., the NAL unit typedescribed with reference to FIG. 39 ) equal to NAL_PREFIX_NSEI and/orNAL_SUFFIX_NSEI. nal_unit_type is the same as or similar to thatdescribed with reference to FIG. 39 .

The VPCCAPSBox according to the embodiments may contain VPCC atlasparameter set structure information (VPCCAPSStruct( ). VPCCAPSStruct( )according to the embodiments may represent information on a V-PCC atlasparameter set (e.g., the V-PCC atlas parameter set described withreference to FIG. 39 ) contained in the file. VPCCAPSStruct( ) accordingto the embodiments may be present at various positions within the file(e.g., the file described with reference to FIGS. 39 and 40 ). Forexample, the VPCCAPSBox may be included in the metadata box for the VPCC(or V3C) bitstream described with reference to FIGS. 24 and 25 . TheVPCCAPSBox according to the embodiments may have the following syntax.

  aligned(8) class VPCCAPSBox extends Box(‘vpap’) { VPCCAPSStruct ( ); }

As described above, VPCCAPSBox may contain VPCCAPSStruct( ).VPCCAPSStruct( ) according to embodiments may represent theabove-described VPCC atlas parameter set structure information.VPCCAPSStruct( ) according to the embodiments may containnumOfAPSArrays, aps_id, aps_NAL_unit_type, aps_numNALUnits, apsLength,and/or apsUnit.

numOfAPSArrays represents the number of atlas parameter sets signaled byVPCCAPSStruct( ) according to the embodiments.

VPCCAPSStruct( ) according to the embodiments may further containaps_id, aps_NAL_unit_type, and aps_numNALUnits based on index j. Index jmay have a value greater than or equal to 0 and less than the valueindicated by numOfAPSArrays.

aps_id indicates an identifier for identifying an atlas parameter setsignaled by VPCCAPSStruct( ) according to the embodiments.

aps_NAL_unit_type indicates the type of the NAL units including theatlas parameter set signaled by VPCCAPSStruct( ) according to theembodiments. For example, aps_NAL_unit_type indicates NAL_ASPS,NALS_AFPS, and/or NAL_AAOS described above with reference to FIG. 39 .

aps_numNALUnits indicates the number of NAL units of a NAL unit typeidentified by the above-described aps_NAL_unit_type.

VPCCAPSStruct( ) according to the embodiments may further containapsLength and apsUnit based on index i. Index i according to theembodiments may have a value greater than or equal to 0 and less thanthe value indicated by aps_numNALUnits.

apsLength indicates the length in bytes of an NAL unit of a NAL unittype identified by the above-described aps_NAL_unit_type.

apsUnit may contain an NAL unit of a NAL unit type identified by theabove-described aps_NAL_unit_type.

As the point cloud data transmission device according to the embodimentsencapsulates the point cloud data using the method described above, thereception device may efficiently access the point cloud bitstream.Furthermore, this configuration may allow the reception device toefficiently process the data of a point cloud bitstream and effectivelyaccess information necessary for rendering, thereby reducing delaysoccurring during decoding and rendering of point cloud data.

FIG. 43 shows VPCC SEI message structure information and atlas aparameter set structure according to embodiments

FIG. 43 shows an example in which an SEI message and/or an atlasparameter set according to embodiments is stored in a sample group(e.g., the sample group described above with reference to FIG. 39 ). Asdescribed above, the V-PCC track (e.g., the V-PCC track of FIG. 38 , thetrack for atlas data of FIG. 41 ) according to the embodiments maycontain one or more samples (e.g., the samples described with referenceto FIG. 39 ). The samples according to the embodiments may be groupedinto a sample group based on the grouping_type. That is, thegrouping_type represents the assignment of samples to a sample group.

Part 4200 shows a case where the above-described grouping type is‘yaps’.

As described above, the sample grouping based on the grouping_type equalto ‘yaps’ may represent the assignment of samples contained in a track(e.g., the V-PCC track described with reference to FIG. 39 ) to an atlasparameter set (e.g., the atlas parameter set described above withreference to FIG. 39 ) carried in the sample group. In addition, thesample grouping based on grouping_type equal to ‘yaps’ represents theassignment of samples contained in the track to the SEI message (e.g.,the SEI message described above with reference to FIGS. 29 and 37 )carried in the corresponding sample group. The above-described track mayrepresent an atlas sub-bitstream (e.g., a V-PCC track, a V-PCC bitstreamtrack, and/or a V-PCC component).

When a SampleToGroupBox with grouping_type equal to ‘yaps’ is present ina track according to embodiments, SampleGroupDescriptionBox with thesame grouping type may be present. In addition, the track may contain IDinformation for identifying the sample group.

The V-PCC track according to the embodiments may include a trackcontaining SampleToGroupBox with grouping_type equal to ‘yaps’

Referring to the syntax shown in part 4200, SampleGroupDescriptiopnEntryhaving grouping_type equal to ‘yaps’ may contain numOfSetupUnits,setupUnitLength, and/or setupUnit.

numOfSetupUnits specifies the number of setup units signaled in thesample group description described above.

SampleGroupDescriptiopnEntry may further contain setupUnitLength and/orsetupUnit based on index i. Index i may have a value greater than orequal to 0 and less than the value indicated by numOfSetupUnits.

setupUnitLength may indicate the size, in bytes, of the setupUnit field.This field may indicate the size of both the NAL unit header and the NALunit payload, but may not include the information about the size of thefield itself.

setupUnit may indicate a NAL unit of type NAL_ASPS, NAL_AFPS, NAL AAPS,NAL_PREFIX_ESEI, NAL_PREFIX_NSEI, NAL SUFFIX ESEI, and/orNAL_SUFFIX_NSEI. The NAL unit indicated by setupUnit may carry dataassociated with this group of samples. That is, a sample group havinggrouping_type equal to ‘yaps’ according to the embodiments may containat least one of an atlas parameter set or an SEI message.

SampleGroupDescriptiopnEntry may be expressed through the followingsyntax instead of the syntax shown in part 4200.

  aligned(8) class VPCCAtlasParamSampleGroupDescriptionEntry( ) extendsSampleGroupDescriptionEntry(‘vaps’) {  VPCCAPSStruct( ); }

VPCCAPSStruct( ) may contain atlas NAL units carrying atlas parametersets (e.g., atlas sequence parameter sets, atlas frame parameter sets,and/or atlas adaptation parameter sets).

As described above, the sample grouping based on grouping_type equal to‘yaps’ represents the assignment of samples contained in the track tothe SEI message carried in the corresponding sample group. Theabove-described track may represent an atlas sub-bitstream (e.g., aV-PCC track, a V-PCC bitstream track, and/or a V-PCC component).

When a SampleToGroupBox with grouping_type equal to ‘vsei’ is present ina track according to embodiments, SampleGroupDescriptionBox with thesame grouping type may be present. In addition, the track may contain IDinformation for identifying the sample group.

The V-PCC track according to the embodiments may include a trackcontaining SampleToGroupBox with grouping_type equal to ‘vsei’

Referring to the syntax shown in part 4201, SampleGroupDescriptiopnEntryhaving grouping_type equal to ‘vsei’ may contain VPCCSEIInfoStruct( ).

VPCCSEIInfoStruct( ) may contain atlas NAL units carrying an essentialSEI message and/or a non-essential SEI message that are applied to thissample group.

As the point cloud data transmission device according to the embodimentsencapsulates the point cloud data using the method described above, thereception device may efficiently access the point cloud bitstream.Furthermore, this configuration may allow the reception device toefficiently process the data of a point cloud bitstream and effectivelyaccess information necessary for rendering, thereby reducing delaysoccurring during decoding and rendering of point cloud data.

FIG. 44 illustrates a method for an SEI track group and SEI entitygrouping according to embodiments.

FIG. 44 shows exemplary syntax of SpatialRegionGroupBox 43000 requiredto apply SEI track grouping and exemplary syntax ofPlayoutEntityGroupBox 43001 required to apply SEI entity grouping intrack grouping according to embodiments.

SpatialRegionGroupBox and/or PlayoutEntityGroupBox described withreference to FIG. 44 may be encapsulated in a file or in a V-PCC track(e.g., the V-PCC track in FIG. 38 ).

Track grouping according to the embodiments is grouping tracksassociated with each other. That is, one or more tracks included in asingle track group are tracks associated with each other.

VPCCSEIInfoStruct( ) shown in FIG. 44 may represent theVPCCSEIInfoStruct( ) described above with reference to FIG. 42 .VPCCSEIInfoStruct( ) shown in FIG. 44 may contain the data structureshown in FIG. 41 . VPCCSEIInfoStruct( ) shown in FIG. 44 may containatlas NAL units (e.g., the essential SEI message and/or non-essentialSEI described with reference to FIGS. 41 and 42 ) carrying an essentialSEI message and/or a non-essential SEI message applied to tracks of atrack group.

Part 43000 shows exemplary syntax of SpatialRegionGroupBox according tothe embodiments. Part 43001 shows exemplary syntax ofPlayoutEntityGroupBox according to the embodiments.

SEI track grouping (or SEI track group) according to embodiments will bedescribed.

TrackGroupTypeBox with track_group_type equal to ‘vpse’ may indicatethat the corresponding track belongs to a group of tracks that areassociated with SEI messages. Tracks associated with the same SEImessages may have the same value of track_group_id for track_group_type‘vpse’.

TrackGroupTypeBox with track_group_type equal to ‘vpse’ according to theembodiments may be encapsulated (or stored) in a file in the form ofSpatialRegionGroupBox 43000 described above.

SEI entity grouping according to embodiments will be described.

EntityToGroupBox with track_group_type equal to ‘vpse’ may indicate thattracks or items belong to the group associated with SEI messages. TheEntityToGroupTypeBox according to the embodiments may group timed tracksor non-timed items associated with the same SEI message.

EntityToGroupBox with track_group_type equal to ‘vpse’ according to theembodiments may be encapsulated (or stored) in a file in the form ofPlayoutEntityGroupBox. EntityToGroupBox according to the embodiments mayhave the following properties.

-   -   Box Types: ‘vpse’    -   Container: GroupsListBox    -   Mandatory: No    -   Quantity: Zero or more

EntityToGroupBox with track_group_type equal to ‘vpse’ according to theembodiments may contain num_entities_in_group and VPCCSEIInfoStruct( ).VPCCSEIInfoStruct( ) is the same as that described above.num_entities_in_group according to the embodiments indicates the numberof entities included in (corresponding to) the entity group.

The above-described SpatialRegionGroupBox and PlayoutEntityGroupBox mayfurther contain an atlas parameter set in addition to the SEI message.

The point cloud data transmission device according to the embodimentsmay transmit the VPCCSEIInfoStruct( ) to the reception device using theabove-described method, thereby allowing the reception device toeffectively play back point cloud videos or images and enabling users tointeract with the point cloud videos or images.

With this configuration, the point cloud data transmission deviceaccording to the embodiments may efficiently store and signal a V-PCCbitstream by dividing the same into one or more tracks in a file, andefficiently signal the relationship between multiple tracks for thestored V-PCC bitstream. In addition, it may efficiently store andtransmit a file of a point cloud bitstream through identification of analternative V-PCC track stored in the file.

FIG. 45 illustrates a method for atlas parameter set track grouping (SEItrack group) and atlas parameter set entity grouping (SEI entitygrouping) according to embodiments.

FIG. 45 shows exemplary syntax of SpatialRegionGroupBox 44000 requiredto apply atlas parameter set (or APS) track grouping and exemplarysyntax of PlayoutEntityGroupBox 44001 required to apply APS entitygrouping in track grouping according to embodiments.SpatialRegionGroupBox and/or PlayoutEntityGroupBox described withreference to FIG. 45 may be encapsulated in a file or in a V-PCC track(e.g., the V-PCC track in FIG. 38 ).

The track grouping according to the embodiments is the same as orsimilar to that described above with reference to FIG. 42 .

VPCCAPSStruct( ) shown in FIG. 45 may represent the VPCCAPSStruct( )described above with reference to FIG. 42 . VPCCAPSStruct( ) shown inFIG. 45 may contain atlas NAL units including an atlas parameter setapplied to the tracks of the track group (e.g., the atlas sequenceparameter set of FIG. 30 , the atlas frame parameter set of FIG. 31and/or the atlas adaptation parameter set of FIG. 33 ).

Part 44000 shows exemplary syntax of SpatialRegionGroupBox according tothe embodiments. Part 44001 shows exemplary syntax ofPlayoutEntityGroupBox according to the embodiments.

Atlas parameter set track grouping according to the embodiments will bedescribed.

TrackGroupTypeBox with track_group_type equal to ‘vpap’ according to theembodiments indicates that the corresponding track belongs to a group oftracks that are associated with atlas parameter sets. Tracks associatedwith the same atlas parameter sets have the same value of track_group_idfor track_group_type ‘vpap’. track_group_id according to the embodimentsmay be an identifier for identifying a track group.

TrackGroupTypeBox with track_group_type equal to ‘vpap’ according to theembodiments may be encapsulated (or stored) in a file in the form ofSpatialRegionGroupBox 44000 described above.

Atlas parameter set entity grouping according to the embodiments will bedescribed.

EntityToGroupBox with track_group_type equal to ‘vpap’ may indicate thattracks or items belong to the group associated with atlas parametersets. The EntityToGroupTypeBox according to the embodiments may grouptimed tracks or non-timed items associated with the same atlas parameterset.

EntityToGroupBox with track_group_type equal to ‘vpap’ according to theembodiments may be encapsulated (or stored) in a file in the form ofPlayoutEntityGroupBox. EntityToGroupBox according to the embodiments mayhave the following properties.

-   -   Box Types: ‘vpap’    -   Container: GroupsListBox    -   Mandatory: No    -   Quantity: Zero or more

EntityToGroupBox with track_group_type equal to ‘vpap’ according to theembodiments may contain num_entities_in_group and VPCCAPSStruct( ).VPCCAPSStruct( ) is the same as that described above.num_entities_in_group according to the embodiments indicates the numberof entities included in (corresponding to) the entity group.

The above-described SpatialRegionGroupBox and PlayoutEntityGroupBox mayfurther contain an SEI message in addition to the atlas parameter set.

The point cloud data transmission device according to the embodimentsmay transmit the VPCCAPSStruct( ) to the reception device using theabove-described method, thereby allowing the reception device toeffectively play back point cloud videos or images and enabling users tointeract with the point cloud videos or images.

With this configuration, the point cloud data transmission deviceaccording to the embodiments may efficiently store and signal a V-PCCbitstream by dividing the same into one or more tracks in a file, andefficiently signal the relationship between multiple tracks for thestored V-PCC bitstream. In addition, it may efficiently store andtransmit a file of a point cloud bitstream through identification of analternative V-PCC track stored in the file.

FIG. 46 shows an example of a V-PCC sample entry and a V-PCC bitstreamsample entry (VPCCBitstreamSampleEntry) according to embodiments.

FIG. 46 illustrates an exemplary method of storing an SEI message and anatlas parameter set in a sample entry (e.g., the sample entry describedabove with reference to FIGS. 38, 39, and 41 ) according to embodiments.Part 45000 shows exemplary syntax of a V-PCC sample entry according tothe embodiments. Part 45001 shows exemplary syntax of the V-PCCbitstream sample entry (VPCCBitstreamSampleEntry) according to theembodiments. The V-PCC sample entry and the V-PCC bitstream sample entryare the same as or similar to those described with reference to FIG. 39.

The V-PCC sample entry according to the embodiments may have the syntaxstructure shown in part 45000 by, for example, a multi-track containerbased encapsulation (e.g., encapsulation based on the multi-trackcontainer shown in FIG. 39 ).

Referring to the syntax structure shown in part 45000, VPCCSampleEntryaccording to the embodiments may contain includes config indicatingVPCCConfigurationBox, unit_header indicating VPCCUnitHeaderBox.

The VPCCSampleEntry 45000 according to the embodiments may furthercontain VPCCSEIInfoBox and/or VPCCAPSBox. The VPCCSEIInfoBox accordingto the embodiments may contain information on NAL units carrying anessential SEI message and/or a non-essential SEI message applied tosamples referenced by a V-PCC sample entry. The essential SEI messageand/or non-essential SEI message are the same as or similar to thosedescribed above with reference to FIGS. 39 and 41 . The VPCCAPSBoxaccording to the embodiments may contain information on NAL unitscarrying an atlas parameter set (e.g., an atlas sequence parameter set,an atlas frame parameter set, and/or an atlas adaptation parameter set)applied to samples referenced by the V-PCC sample entry). The atlasparameter set is the same as or similar to that described with referenceto FIGS. 39 and 45 .

That is, the VPCCSampleEntry 45000 may further contain VPCCSEIInfoBoxand/or VPCCAPSBox to indicate an SEI message atlas parameter set forV-PCC content corresponding to (i.e., being a target of)VPCCSampleEntry.

The V-VPCCSampleEntry according to the embodiments may have the syntaxstructure shown in 45001 by, for example, single-track container basedencapsulation (e.g., the single-track container based encapsulationshown in FIG. 39 ).

Referring to the syntax structure shown in part 45001, VPCCSampleEntryaccording to the embodiments may contain only config informationindicating VPCCConfigurationBox. The VPCCSampleEntry may be referred toas VPCCBitstreamSampleEntry.

The VPCCBitstreamSampleEntry 45001 according to the embodiments mayfurther contain VPCCSEIInfoBox and/or VPCCAPSBox. The VPCCSEIInfoBoxand/or VPCCAPSBox are the same as or similar to those described above.

That is, the VPCCSampleEntry 45001 may further contain VPCCSEIInfoBoxand/or VPCCAPSBox. That is, the sample entry described in this drawingmay contain at least one of an SEI message or an atlas parameter setaccording to the embodiments.

encapsulates the point cloud data using the method described above, thereception device may efficiently access the point cloud bitstream.Furthermore, this configuration may allow the reception device toefficiently process the data of a point cloud bitstream and effectivelyaccess information necessary for rendering, thereby reducing delaysoccurring during decoding and rendering of point cloud data.

FIG. 47 shows syntax of a V-PCC SEI sample and/or a V-PCC APS sample bya timed metadata track according to embodiments.

FIG. 47 illustrates an exemplary method of storing an SEI message and anatlas parameter set in a timed metadata track according to embodiments.Part 46000 a shows exemplary syntax of a V-PCC SEI sample entry carriedby a timed metadata track according to embodiments. Part 46001 a showsexemplary syntax of a V-PCC APS sample entry carried by a timed metadatatrack according to the embodiments. Part 46000 b shows exemplary syntaxof a V-PCC SEI sample contained in a timed metadata track according tothe embodiments. Part 46001 b shows exemplary syntax of a V-PCC APSsample contained in a timed metadata track according to the embodiments.The purpose for the timed metadata track may be indicated by the tracksample entry type.

The VPCC SEI timed metadata track will be described.

The dynamic VPCC SEI timed metadata track according to the embodimentsmay indicate whether an essential SEI message and/or a non-essential SEImessage (e.g., the essential SEI message and/or non-essential SEImessage described with reference to FIG. 41 ) dynamically changes overtime. The dynamic VPCC SEI timed metadata track according to theembodiments may be linked to the respective tracks (e.g., a VPCC track,a VPCC bitstream track, and/or a VPCC component track) through the‘cdsc’ track reference.

Referring to the syntax structure shown in part 46000 a, the V-PCC SEIsample entry carried by the VPCC SEI timed metadata track may containVPCCSEIInfoStruct( ). The VPCCSEIInfoStruct( ) according to theembodiments may be the same as or similar to the VPCCSEIInfoStrct( )described with reference to FIGS. 42 and 43 . The VPCCSEIInfoStrct( )according to the embodiments may contain information on an SEI messageapplied to VPCC content corresponding to the above-described VPCC SEItimed metadata track.

The syntax shown in part 46000 b represents the syntax of the VPCC SEIsample carried by the VPCC SEI timed metadata track. That is, the syntaxof a sample described in part 46000 b may represent the syntax of asample contained in the VPCC SEI timed metadata track.

The syntax of the VPCC SEI sample according to the embodiments mayinclude num_active_sei, addl_active_sei, essential_flag,active_sei_type, and/or VPCCSEIInfoStrct( ).

num_active_sei) specifies the number of SEI messages (or active SEImessages) of VPCCSEIInfoStrct( ) according to the embodiments signaledin the VPCCSEISampleEntry. The value of this parameter equal to 0indicates that no SEI message of the sample entry is active.

addl_active_sei equal to 1 specifies that an additionally active SEImessage is directly signaled in the sample through VPCCSEIInfoStrct( ).The value of this parameter equal to 0 specifies that no additionalactive SEI messages are signaled in the sample directly.

The syntax of the VPCC SEI sample according to the embodiments mayfurther contain essential_flag and/oractive_sei_type based on index i.Index i may be greater than or equal to 0, and may be less than thevalue indicated by num_active_sei.

essential_flag equal to 1 indicates that the SEI message is an essentialSEI message (e.g., the essential SEI message described with reference toFIG. 41 ). essential_flag equal to 0 indicates that the SEI message isanon-essential SEI message (e.g., the non-essential SEI messagedescribed with reference to FIG. 41 ).

active_sei_type indicates the type of the active SEI message.active_sei_type indicates the type of an essential SEI message and/ornon-essential SEI message that is signaled from the VPCCSEISampleEntryand is currently active.

The syntax of the VPCC SEI sample according to the embodiments mayfurther contain VPCCSEIInfoStrct( ) corresponding to addl_active_seiindicating 1.

VPCCSEIInfoStrct( ) indicates information on an additional active SEImessage signaled directly in the sample.

The VPCC APS timed metadata track will be described.

The dynamic VPCC APS timed metadata track according to the embodimentsmay indicate whether the atlas parameter set according to theembodiments dynamically changes over time. The dynamic VPCC APS timedmetadata track according to the embodiments may be linked to therespective tracks (e.g., a VPCC track, a VPCC bitstream track, and/or aVPCC component track) through the ‘cdsc’ track reference.

Referring to the syntax structure shown in part 46001 a, theVPCCAPSSampleEntry carried by the VPCC APS timed metadata track maycontain VPCCAPSStruct( ). VPCCAPSStruct( ) according to the embodimentsmay be the same as or similar to VPCCAPSStruct( ) described withreference to FIGS. 42 and 45 . VPCCAPSStruct( ) according to theembodiments may include information on an atlas parameter set applied toVPCC content corresponding to the above-described VPCC APS timedmetadata track.

The syntax shown in part 46001 b represents the syntax of VPCCAPSSamplecarried by the VPCC APS timed metadata track. That is, the syntax of thesample shown in part 46001 b may represent the syntax of the samplecontained in the VPCC APS timed metadata track.

The syntax of the VPCCAPSSample according to the embodiments may containnumactive_aps, addl_active_aps, active_aps_id, active_aps_type, and/orVPCCAPSStruct( ).

num_active_aps specifies the number of active atlas parameter sets ofVPCCAPSStruct( ) according to embodiments signaled inVPCCAPSSampleEntry. When this parameter has a value of 0, it indicatesthat no atlas parameter sets of the sample entry is active.

addl_active_sei equal to 1 specifies that additional active SEI messagesare signaled in the sample directly through VPCCAPSStruct( ).addl_active_sei equal to 0 indicates that specifies that no additionalactive SEI messages are directly signaled in the sample.

The syntax of the VPCCAPSSample according to the embodiments may furthercontain active_aps_id and/or active_aps_type based on index i. Index imay be greater than or equal to 0, and may be less than the valueindicated by num_active_aps.

active_aps_id indicates the identifier of an active atlas parameter setof VPCCAPSStruct( ) according to the embodiments signaled in the activeVPCCAPSSampleEntry.

active_sei_type indicates the type of the active SEI message. Thisparameter indicates the type of the atlas parameter set that is signaledin the VPCCAPSSampleEntry and is currently active.

The syntax of the VPCCAPSSample according to the embodiments may furthercontain VPCCAPSStruct( ) corresponding to addl_active_aps indicating 1.

VPCCAPSStruct( ) indicates information on an additional active atlasparameter set signaled directly in the sample.

The timed metadata track described in this drawing may contain at leastone of an atlas parameter set or an SEI message according toembodiments.

With this configuration, the point cloud data transmission deviceaccording to the embodiments may efficiently store and signal a V-PCCbitstream by dividing the same into one or more tracks in a file, andefficiently signal the relationship between multiple tracks for thestored V-PCC bitstream. In addition, it may efficiently store andtransmit a file of a point cloud bitstream through identification of analternative V-PCC track stored in the file.

As the point cloud data transmission device according to the embodimentsencapsulates the point cloud data using the method described above, thereception device may efficiently access the point cloud bitstream.Furthermore, this configuration may allow the reception device toefficiently process the data of a point cloud bitstream and effectivelyaccess information necessary for rendering, thereby reducing delaysoccurring during decoding and rendering of point cloud data.

FIG. 48 shows exemplary syntax of a V-PCC SEI item property and a V-PCCAPS item property according to embodiments.

FIG. 48 illustrates an exemplary method of storing an SEI message and anatlas parameter set in an item property according to embodiments.VPCCSEIItemProperty 47000 and VPCCAPSItemProperty, 47001 according tothe embodiments shown in FIG. 48 may be contained in the item describedwith reference to FIG. 21 and/or the V-PCC item described with referenceto FIG. 40 .

VPCCSEIItemProperty may be defined to store static metadata of the SEImessage of the associated V-PCC item. The VPCCSEIItemProperty may havethe following properties.

-   -   Box Types: ‘vpc1’    -   Property Type: Descriptive item property    -   Container: ItemPropertyContainerBox    -   Mandatory (per item): No    -   Quantity (per item): One

VPCCSEIInfoStuct( ) shown in part 47000 may indicate information on anessential SEI message and/or non-essential SEI message associated withthe V-PCC item (e.g., the essential SEI message and/or non-essential SEImessage described with reference to FIG. 41 ). VPCCSEIInfoStuct( ) maybe the same as or similar to the VPCCSEIInfoStrct( ) described withreference to FIGS. 42 to 44 . VPCCSEIItemProperty according to theembodiments may further contain an atlas parameter set in addition tothe SEI message.

The VPCCAPSItemProperty may be defined to store static metadata of theatlas parameter set of the associated V-PCC item. TheVPCCAPSItemProperty may have the following properties.

-   -   Box Type: ‘vpap’    -   Property Type: Descriptive item property    -   Container: ItemPropertyContainerBox    -   Mandatory (per item): No    -   Quantity (per item): One

VPCCAPSStruct( ) shown in part 47001 may indicate information on a VPCCatlas parameter set (e.g., an atlas sequence parameter set, an atlasframe parameter set, and/or an atlas adaptation parameter set)associated with the V-PCC item. VPCCAPSStruct( ) may be the same as orsimilar to the VPCCAPSStruct( ) described with reference to FIGS. 42 and44 . The VPCCAPSItemProperty according to the embodiments may furthercontain an SEI message according to the embodiments in addition to theatlas parameter set.

As the point cloud data transmission device according to the embodimentsencapsulates the point cloud data using the method described above, thereception device may efficiently access the point cloud bitstream.Furthermore, this configuration may allow the reception device toefficiently process the data of a point cloud bitstream and effectivelyaccess information necessary for rendering, thereby reducing delaysoccurring during decoding and rendering of point cloud data.

FIG. 49 is a flowchart illustrating a method of transmitting point clouddata according to embodiments.

FIG. 49 is a flowchart illustrating a method of transmitting point clouddata by a point cloud data transmission device according to embodiments(e.g., the transmission device described above with reference to FIGS.1, 18, 20 to 22, 24, 37, and 39 to 48 ). The transmission deviceaccording to the embodiments may further perform operations other thanthe operations described with reference to FIG. 49 .

The point cloud data transmission method according to the embodimentsmay include encoding point cloud data (S4800), encapsulating the pointcloud data (S4801), and/or transmitting the point cloud data (S4802).

In operation S4800, the point cloud data is encoded. In operation S4800,the point cloud data according to the embodiments is encoded. Forexample, in operation S4801, some or all of the operations of the pointcloud video encoder 10002 of FIG. 1 , the operations shown in FIG. 4 ,the operations of the encoding device 100 of FIG. 15 , the operations ofFIG. 18 , and the video encoding 20002 and/or image encoding 20003 ofFIGS. 20 and 21 may be performed.

In operation S4801, the point cloud data is encapsulated. OperationS4801 may be performed based on a file. The file according to theembodiments is the same as or similar to the file described withreference to FIGS. 1, 2, and 18 to 48 . That is, the transmission deviceaccording to the embodiments may encapsulate the point cloud data basedon the file.

The file according to the embodiments may contain a track for atlas datafor the point cloud data (e.g., the track for atlas data in FIGS. 41 and43 , the V-PCC track described with reference to FIGS. 38 to 45 ). Thetrack (or V-PCC track) for atlas data according to the embodiments maybe a track that carries metadata for the point cloud data.

A sample group (e.g., the sample group of FIG. 43 ) contained in thetrack according to embodiments may include at least one of an atlasparameter set and/or an SEI message for the atlas data. A sample entry(e.g., the sample entry of FIG. 46 ) contained in the track according tothe embodiments may include at least one of an atlas parameter setand/or an SEI message for the atlas data. The atlas parameter set andthe SEI message according to the embodiments are the same as or similarto those described above with reference to FIGS. 38 to 48 .

As the sample group contained in the track according to the embodimentsincludes at least one of the atlas parameter set or the SEI message,grouping type information for the sample group may indicate that atleast one of the atlas parameter set or the SEI message is included inthe sample group. The sample group and grouping type information are thesame as or similar to those described above with reference to FIG. 43 .The grouping type information indicating that at least one of the atlasparameter set or the SEI message is included in the sample groupaccording to the embodiments may indicate ‘yaps’ and/or ‘vsei’ describedabove with reference to FIG. 43 . As the sample entry included in thetrack according to the embodiments includes at least one of the atlasparameter set or the SEI message, the information indicating the type ofthe sample entry may indicate that at least one of the atlas parameterset or the SEI message is included in the sample entry. The informationindicating the type of the sample entry according to embodiments mayindicate the sample entry type described above with reference to FIGS.39 and 46 . The information indicating the type of the sample entryindicating that at least one of the atlas parameter set or the SEImessage is included in the sample entry according to the embodiments mayindicate ‘vpc1’ or ‘vpcg’ described above in FIG. 39 , or ‘vpe1’described above with reference to FIG. 46 . Here, ‘vpc1’, ‘vpcg’, and‘vpe1’ may be referred to as ‘v3c1’, ‘v3cg’ and ‘v3e1’.

The SEI message according to the embodiments may include at least one ofan essential SEI message or a non-essential SEI message. The essentialSEI message or the non-essential SEI message is the same as or similarto those described above with reference to FIGS. 41 to 49 . The fileaccording to the embodiments may further contain VPCC SEI messagestructure information for the SEI message (e.g., the VPCC SEI messagestructure information of FIG. 42 ). The VPCC SEI message structureinformation according to the embodiments may include at least one ofinformation indicating the number of essential SEI messages (e.g.,numEssentialSEIs in FIG. 42 ), information indicating the type of theessential SEI message (e.g., ESEI_type in FIG. 42 ), informationindicating the number of non-essential SEI messages (e.g.,numNonEssentialSEIs in FIG. 42 ), or information indicating the type ofthe non-essential SEI message (e.g., NSEI_type in FIG. 42 ).

The file according to the embodiments may further contain VPCC atlasparameter set structure information for the atlas parameter set. TheVPCC atlas parameter set structure information is the same as or similarto that described above with reference to FIG. 42 . The VPCC atlasparameter set structure information according to the embodiments mayinclude information about the number of atlas parameters (e.g.,numOfAPSArrays in FIG. 42 ) and/or information for identifying the atlasparameter set (e.g. aps_id in FIG. 42 ).

In the operation of transmitting the point cloud data (S4802), theencapsulated file according to the embodiments is transmitted to thepoint cloud data reception device.

As the point cloud data transmission device according to the embodimentstransmits the point cloud data using the method described above, thereception device may efficiently access the point cloud bitstream.Furthermore, this configuration may allow the reception device toefficiently process the data of a point cloud bitstream and effectivelyaccess information necessary for rendering, thereby reducing delaysoccurring during decoding and rendering of point cloud data.

FIG. 50 is a flowchart illustrating a method of receiving point clouddata according to embodiments.

FIG. 50 is a flowchart illustrating a method of receiving point clouddata by a point cloud data reception device according to embodiments(e.g., the reception device described in FIGS. 1, 3, 19 to 23 and 37 to48 ). The reception device according to the embodiments may furtherperform operations other than the operations described with reference toFIG. 50 .

The point cloud data reception method according to the embodiments mayinclude receiving point cloud data (S4900), decapsulating the pointcloud data (S4901), and/or decoding the point cloud data (S4902).

In operation S4900, the point cloud data is received. In operationS4900, the file described with reference to FIG. 47 is received. Inoperation S4900, may perform some or all of the operations of thereceiver 10006 of FIG. 1 , the receiver of FIG. 19 , and the delivery ofFIG. 20 or 22 .

In operation S4901, the point cloud data is decapsulated. In operationS4801, some or all of the operations of the file/segment decapsulationmodule 10007 of FIG. 1 and the file/segment decapsulators 20005 and22000 of FIGS. 20 and 22 may be performed. Operation S4901 may beperformed based on a file. The file according to the embodiments is thesame as or similar to the file described with reference to FIGS. 1, 2,and 18 to 48 . That is, the reception device according to theembodiments may decapsulate the point cloud data based on the file.

The file according to the embodiments may contain a track for atlas datafor the point cloud data (e.g., the track for atlas data in FIGS. 41 and43 , the V-PCC track described with reference to FIGS. 38 to 45 ). Thetrack (or V-PCC track) for atlas data according to the embodiments maybe a track that carries metadata for the point cloud data.

A sample group (e.g., the sample group of FIG. 43 ) contained in thetrack according to embodiments may include at least one of an atlasparameter set and/or an SEI message for the atlas data. A sample entry(e.g., the sample entry of FIG. 46 ) contained in the track according tothe embodiments may include at least one of an atlas parameter setand/or an SEI message for the atlas data. The atlas parameter set andthe SEI message according to the embodiments are the same as or similarto those described above with reference to FIGS. 38 to 48 .

As the sample group contained in the track according to the embodimentsincludes at least one of the atlas parameter set or the SEI message,grouping type information for the sample group may indicate that atleast one of the atlas parameter set or the SEI message is included inthe sample group. The sample group and grouping type information are thesame as or similar to those described above with reference to FIG. 43 .The grouping type information indicating that at least one of the atlasparameter set or the SEI message is included in the sample groupaccording to the embodiments may indicate ‘yaps’ and/or ‘vsei’ describedabove with reference to FIG. 43 . As the sample entry included in thetrack according to the embodiments includes at least one of the atlasparameter set or the SEI message, the information indicating the type ofthe sample entry may indicate that at least one of the atlas parameterset or the SEI message is included in the sample entry. The informationindicating the type of the sample entry according to embodiments mayindicate the sample entry type described above with reference to FIGS.39 and 46 . The information indicating the type of the sample entryindicating that at least one of the atlas parameter set or the SEImessage is included in the sample entry according to the embodiments mayindicate ‘vpc1’ or ‘vpcg’ described above in FIG. 39 , or ‘vpe1’described above with reference to FIG. 46 . Here, ‘vpc1’, ‘vpcg’, and‘vpe1’ may be referred to as ‘v3c1’, ‘v3cg’ and ‘v3e1’.

The SEI message according to the embodiments may include at least one ofan essential SEI message or a non-essential SEI message. The essentialSEI message or the non-essential SEI message is the same as or similarto those described above with reference to FIGS. 41 to 49 . The fileaccording to the embodiments may further contain VPCC SEI messagestructure information for the SEI message (e.g., the VPCC SEI messagestructure information of FIG. 42 ). The VPCC SEI message structureinformation according to the embodiments may include at least one ofinformation indicating the number of essential SEI messages (e.g.,numEssentialSEIs in FIG. 42 ), information indicating the type of theessential SEI message (e.g., ESEI_type in FIG. 42 ), informationindicating the number of non-essential SEI messages (e.g.,numNonEssentialSEIs in FIG. 42 ), or information indicating the type ofthe non-essential SEI message (e.g., NSEI_type in FIG. 42 ).

The file according to the embodiments may further contain VPCC atlasparameter set structure information for the atlas parameter set. TheVPCC atlas parameter set structure information is the same as or similarto that described above with reference to FIG. 42 . The VPCC atlasparameter set structure information according to the embodiments mayinclude information about the number of atlas parameters (e.g.,numOfAPSArrays in FIG. 42 ) and/or information for identifying the atlasparameter set (e.g. aps_id in FIG. 42 ).

In operation S4902, the point cloud data is decoded. In operation S4902,some or all of the operations of the point cloud video decoder 10008 ofFIG. 1 , the V-PCC decoding operations of FIG. 16 , the operations ofFIG. 19 , the video decoding and image decoding 20006 of FIG. 20 , thevideo decoding 22001 of FIG. 22 , or the image decoding 22002.

The embodiments have been described in terms of a method and/or adevice. The description of the method and the description of the devicemay complement each other.

Although embodiments have been described with reference to each of theaccompanying drawings for simplicity, it is possible to design newembodiments by merging the embodiments illustrated in the accompanyingdrawings. If a recording medium readable by a computer, in whichprograms for executing the embodiments mentioned in the foregoingdescription are recorded, is designed by those skilled in the art, itmay also fall within the scope of the appended claims and theirequivalents. The devices and methods may not be limited by theconfigurations and methods of the embodiments described above. Theembodiments described above may be configured by being selectivelycombined with one another entirely or in part to enable variousmodifications. Although preferred embodiments have been described withreference to the drawings, those skilled in the art will appreciate thatvarious modifications and variations may be made in the embodimentswithout departing from the spirit or scope of the disclosure describedin the appended claims. Such modifications are not to be understoodindividually from the technical idea or perspective of the embodiments.

Various elements of the devices of the embodiments may be implemented byhardware, software, firmware, or a combination thereof. Various elementsin the embodiments may be implemented by a single chip, for example, asingle hardware circuit. According to embodiments, the componentsaccording to the embodiments may be implemented as separate chips,respectively. According to embodiments, at least one or more of thecomponents of the device according to the embodiments may include one ormore processors capable of executing one or more programs. The one ormore programs may perform any one or more of the operations/methodsaccording to the embodiments or include instructions for performing thesame. Executable instructions for performing the method/operations ofthe device according to the embodiments may be stored in anon-transitory CRM or other computer program products configured to beexecuted by one or more processors, or may be stored in a transitory CRMor other computer program products configured to be executed by one ormore processors. In addition, the memory according to the embodimentsmay be used as a concept covering not only volatile memories (e.g., RAM)but also nonvolatile memories, flash memories, and PROMs. In addition,it may also be implemented in the form of a carrier wave, such astransmission over the Internet. In addition, the processor-readablerecording medium may be distributed to computer systems connected over anetwork such that the processor-readable code may be stored and executedin a distributed fashion.

In this document, the term “I” and “,” should be interpreted asindicating “and/or.” For instance, the expression “A/B” may mean “Aand/or B.” Further, “A, B” may mean “A and/or B.” Further, “A/B/C” maymean “at least one of A, B, and/or C.” “A, B, C” may also mean “at leastone of A, B, and/or C.” Further, in the document, the term “or” shouldbe interpreted as “and/or.” For instance, the expression “A or B” maymean 1) only A, 2) only B, and/or 3) both A and B. In other words, theterm “or” in this document should be interpreted as “additionally oralternatively.”

Terms such as first and second may be used to describe various elementsof the embodiments. However, various components according to theembodiments should not be limited by the above terms. These terms areonly used to distinguish one element from another. For example, a firstuser input signal may be referred to as a second user input signal.Similarly, the second user input signal may be referred to as a firstuser input signal. Use of these terms should be construed as notdeparting from the scope of the various embodiments. The first userinput signal and the second user input signal are both user inputsignals, but do not mean the same user input signal unless contextclearly dictates otherwise.

The terminology used to describe the embodiments is used for the purposeof describing particular embodiments only and is not intended to belimiting of the embodiments. As used in the description of theembodiments and in the claims, the singular forms “a”, “an”, and “the”include plural referents unless the context clearly dictates otherwise.The expression “and/or” is used to include all possible combinations ofterms. The terms such as “includes” or “has” are intended to indicateexistence of figures, numbers, steps, elements, and/or components andshould be understood as not precluding possibility of existence ofadditional existence of figures, numbers, steps, elements, and/orcomponents. As used herein, conditional expressions such as “if” and“when” are not limited to an optional case and are intended to beinterpreted, when a specific condition is satisfied, to perform therelated operation or interpret the related definition according to thespecific condition.

Operations according to the embodiments described in this specificationmay be performed by a transmission/reception device including a memoryand/or a processor according to embodiments. The memory may storeprograms for processing/controlling the operations according to theembodiments, and the processor may control various operations describedin this specification. The processor may be referred to as a controlleror the like. In embodiments, operations may be performed by firmware,software, and/or combinations thereof. The firmware, software, and/orcombinations thereof may be stored in the processor or the memory.

The operations according to the above-described embodiments may beperformed by the transmission device and/or the reception deviceaccording to the embodiments. The transmission/reception device mayinclude a transmitter/receiver configured to transmit and receive mediadata, a memory configured to store instructions (program code,algorithms, flowcharts and/or data) for the processes according to theembodiments, and a processor configured to control the operations of thetransmission/reception device.

The processor may be referred to as a controller or the like, and maycorrespond to, for example, hardware, software, and/or a combinationthereof. The operations according to the above-described embodiments maybe performed by the processor. In addition, the processor may beimplemented as an encoder/decoder for the operations of theabove-described embodiments.

MODE FOR THE DISCLOSURE

As described above, related details have been described in the best modefor carrying out the embodiments.

INDUSTRIAL APPLICABILITY

As described above, the embodiments are fully or partially applicable toa point cloud data transmission/reception device and system.

Those skilled in the art may change or modify the embodiments in variousways within the scope of the embodiments.

Embodiments may include variations/modifications within the scope of theclaims and their equivalents.

What is claimed is:
 1. A method for transmitting point cloud data, themethod comprising: encoding point cloud data; encapsulating the pointcloud data based on a file; and transmitting the file, wherein the fileincludes a track for atlas data for the point cloud data and a componenttrack including the point cloud data, wherein the track includes atlasparameter sample group information having a grouping type having anidentifier for the sample group, wherein the atlas parameter samplegroup information includes information for representing a number ofsetup units in the atlas parameter sample group information, and thesetup units include at least one of an atlas sequence parameterset(ASPS), an atlas adaptation parameter set(AAPS), an atlas frameparameter set(AFPS), an essential supplemental enhancementinformation(ESEI), a non-essential supplemental enhancementinformation(NSEI), and wherein the atlas parameter sample groupinformation is identified based on the grouping type.
 2. An apparatusfor transmitting point cloud data, the apparatus comprising: an encoderconfigured to encode point cloud data; an encapsulator configured toencapsulate the point cloud data based on a file; and a transmitterconfigured to transmit the file, wherein the file includes a track foratlas data for the point cloud data and a component track including thepoint cloud data, wherein the track includes atlas parameter samplegroup information having a grouping type having an identifier for asample group, wherein the atlas parameter sample group informationincludes information for representing a number of setup units in theatlas parameter sample group information, and the setup units include atleast one of an atlas sequence parameter set(ASPS), an atlas adaptationparameter set(AAPS), an atlas frame parameter set(AFPS), an essentialsupplemental enhancement information(ESEI), a non-essential supplementalenhancement information(NSEI), and wherein the atlas parameter samplegroup information is identified based on the grouping type.
 3. A methodfor receiving point cloud data, the method comprising: receiving a fileincluding point cloud data; decapsulating the file; decoding the pointcloud data; and wherein the file includes a track for atlas data for thepoint cloud data and a component track including the point cloud data,wherein the track includes atlas parameter sample group informationhaving a grouping type having an identifier for a sample group, whereinthe atlas parameter sample group information includes information forrepresenting a number of setup units in the atlas parameter sample groupinformation, and the setup units include at least one of an atlassequence parameter set(ASPS), an atlas adaptation parameter set(AAPS),an atlas frame parameter set(AFPS), an essential supplementalenhancement information(ESEI), a non-essential supplemental enhancementinformation(NSEI), and wherein the atlas parameter sample groupinformation is identified based on the grouping type.
 4. An apparatusfor receiving point cloud data, the apparatus comprising: a receiverconfigured to receive a file including point cloud data; a decapsulatorconfigured to decapsulate the file; a decoder configured to decode thepoint cloud data; and wherein the file includes a track for atlas datafor the point cloud data and a component track including the point clouddata, wherein the track includes atlas parameter sample groupinformation having a grouping type having an identifier for a samplegroup, wherein the atlas parameter sample group information includesinformation for representing a number of setup units in the atlasparameter sample group information, and the setup units include at leastone of an atlas sequence parameter set(ASPS), an atlas adaptationparameter set(AAPS), an atlas frame parameter set(AFPS), an essentialsupplemental enhancement information(ESEI), a non-essential supplementalenhancement information(NSEI), and wherein the atlas parameter samplegroup information is identified based on the grouping type.
 5. Themethod of claim 1, wherein the atlas parameter sample group informationincludes type information for representing a type of the setup units. 6.The apparatus of claim 2, wherein the atlas parameter sample groupinformation includes type information for representing a type of thesetup units.
 7. The method of claim 3, wherein the atlas parametersample group information includes type information for representing atype of the setup units.
 8. The apparatus of claim 4, wherein the atlasparameter sample group information includes type information forrepresenting a type of the setup units.